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• Magento Apache Config & Memory Issues

  - by cheshirepine

  I have a Magento installation on a VPS that is giving me a headache. This particular VPS has a reasonable spec - 2gb Memory and 50gb storage. It runs a single domain, with a single Magento install - and nothing else. About 5 months ago we started having issues. Every so often (about once every 2 or 3 weeks) the VPS would crash - all processes stopped and the only way to restart the container is via Virtuozzo. Now, however its 2 or 3 times a week. My VPS hosts confirm I am breaching the 2gb memory limit, at which point all VPS processes are killed to stop it bringing the entire node down. I have not made any config changes to it at all - I was running New Relic on it for a short while, but have removed that in case it was contributing to the issues. I can see nothing in the logs which indicates an issue and we have no CRON jobs running at the time the crashes happen. The site generates steady, but not huge amounts of traffic (averaging usually less than 100 visits per day) Is there anything in particular I should have done to the Apache or PHP configs to help? Im not a massivley experienced Apache admin, but know more than enough to solve most problems... Failing that, any other ideas that might help? Can't afford for this site to be down this much.

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• Exim and receiving email with large recipient lists

  - by AceJordin

  I have Exim4 running on Debian configured to receive mail on multiple domains. Exim is set to forward all email that is received to one of the domains to another box. This box is configured with a catchall mailbox that everything goes in. My issue is that when an email is sent to the domain, which contains a large amount of addresses (all to the same domain, but different users), Exim will receive the single email over multiple connections. This means that the catchall mailbox receives multiple copies of the single email all containing the full recipient list. For example, I was able to reproduce it by sending an email from my gmail account that contained 500 recipients (eg [email protected]; [email protected]; [email protected]; etc. for a total of 500). Exim received the message as 20 messages (25 recipients per; appears to be a gmail server setting). So the catchall mailbox received 20 messages, each containing all 500 addresses. I'm pretty sure I understand why this is happening but is there any way I can configure Exim to only receive it once, or to combine it into one? Is there anything that can be done on my end, or am I at the mercy of the sending email server? This is causing havoc with a process that polls the catchall mailbox and parses each recipient in each email.

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• OS X AFP shares and access

  - by gbrandt

  I am running 10.5.6 Client as a mini server and am having problems with AFP shares. All clients are OS X 10.5.7 I have created three users for 'File Sharing' only on the 'server'. I have created groups and placed these users into specific groups. I have created ACL's to give each group access to certain shares. Two of those users can read and write to any share, one user cannot write to the shares, with different results: when copying a directory, only the directory is created, no files inside are copied, the OS does not give any errors when copying a single file I get three dialogs: "You may need to enter the name and password for an administrator on this computer to change the item named 'xxxx', "The item 'xxxxx' contains one or more items you do not have permission to read. Do you want to copy the items you are allowed to read?, and, The operation cannot be completed because you do not have sufficient priveleges for some of the items. With the single file, a file gets created on the server, but is empty. My ACL for the group this user belongs to is: 0: group:projectmembers allow list,add_file,search,delete,add_subdirectory,delete_child,readattr,writeattr,readextattr,writeextattr,readsecurity,file_inherit,directory_inherit 1: group:informationtechnology inherited allow list,add_file,search,delete,add_subdirectory,delete_child,readattr,writeattr,readextattr,writeextattr,readsecurity,file_inherit,directory_inherit 2: group:executive inherited allow list,add_file,search,delete,add_subdirectory,delete_child,readattr,writeattr,readextattr,writeextattr,readsecurity,file_inherit,directory_inherit 3: group:everyone inherited deny list,add_file,search,delete,add_subdirectory,delete_child,readattr,writeattr,readextattr,writeextattr,readsecurity,file_inherit,directory_inherit User 1 & 2 belong to informationtechnology and executive and projectmembers, they can read and write freely on the share. User 3 belongs to projectmembers and cannot read and write freely. I have read that this is a UID issue, however User 1 & 2 do not have matching UID's across clients and server and they work, so I don't think this is the case. Any ideas?

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• Is it the address bus size or the data bus size that determines "8-bit , 16-bit ,32-bit ,64-bit " systems?

  - by learner

  My simple understanding is as follows. Memory (RAM) is composed of bits, groups of 8 which form bytes, each of which can be addressed ,and hence byte addressable memory. Address Bus stores the location of a byte of memory. If an address bus is of size 32 bits, that means it can hold upto 232 numbers and it hence can refer upto 232 bytes of memory = 4GB of memory and any memory greater than that is useless. Data bus is used to send the value to be written to/read off the memory. If I have a data bus of size 32 bits, it means a maximum of 4 bytes can be written to/read off the memory at a time. I find no relation between this size and the maximum memory size possible. But I read here that: Even though most systems are byte-addressable, it makes sense for the processor to move as much data around as possible. This is done by the data bus, and the size of the data bus is where the names 8-bit system, 16-bit system, 32-bit system, 64-bit system, etc.. come from. When the data bus is 8 bits wide, it can transfer 8 bits in a single memory operation. When the data bus is 32 bits wide (as is most common at the time of writing), at most, 32 bits can be moved in a single memory operation. This says that the size of the data bus is what gives an OS the name, 8bit, 16bit and so on. What is wrong with my understanding?

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• Best option for storage clustering

  - by sam

  I'm working on an application that requires a large amount of storage space and I want to handle storage 'in-house' (Much cheaper than, say, S3) so we will have multiple servers (Initially 4) with large amounts of storage (6TB each). The storage will need to be very flexible and configurable, each piece of data should be replicated on at least 2 servers and must be easily readable/writable from ether an API of a UNIX device/file/folder like a normal drive, I don't mind which. We must also be able to easily offload content to our HTTP CDN (Edgecast), it doesn't need to have built in HTTP support but if it doesn't I'm going to have to write something to get the files onto HTTP so they can be pulled by the CDN. I've looked at a lot of solutions including Eucalyptus Walrus OpenStack Object Storage MogileFS and some others which I can't remember All the servers will be running RHEL 6, they have 4x1.5TB drives which will be RAID1'd into a single partition. All the servers have 1GB/s connections between them and 100MB/s connections to the internet with unlimited bandwidth. They have 2x2.66ghz processors. I understand there isn't a single, perfect answer but it would be nice to get some pointers.

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• Azure load-balancing strategy

  - by growse

  I'm currently building out a small web deployment using VM instances on MS Azure. The main problem I'm facing at the moment is trying to figure out how to get the load-balancing to detect if a particular VM has failed and not route traffic to that VM. As far as I can tell, there are only only two load-balancing options: Have multiple VMs (web01, web02, web03 etc.) within the same 'cloud service' behind a single VIP, and configure the endpoints to be load balanced. Create multiple 'cloud services', put a single web VM in each and create a traffic manager service across all these services. It appears that (1) is extremely simplistic and doesn't attempt to do any host failure detection. (2) appears to be much more varied, but requires me to put all my webservers in their own individual cloud service. Traffic manager appears to be much more directed at a geographic failover scenario, where you have multiple cloud services across different regions. This approach also has the disadvantage in that my web servers won't be able to communicate with my databases on internal IP addresses, unlike scenario (1). What's the best approach here?

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• Confused about the Windows 7 Preinstallation Kit

  - by David Brown

  I build custom PCs and would like to use the Windows 7 Preinstallation Kit to make installation go a little quicker and customize the Windows image. However, since each PC is built to a particular customer's specifications, the hardware will rarely be the same. So, I would like to have a single answer file that will work for everything. I'm not sure if that's possible, however. What I mostly want to do for now is add my support information as well as pre-set anything that I would normally change after each installation completes. I have a Windows 7 Professional Upgrade DVD set (both 32-bit and 64-bit), but no OEM disks. I copied the Install.wim file to my local drive and opened it in the Windows System Image Manager, but it asks me to choose a catalog file specifically for each edition of Windows 7. Will this limit the answer file to whichever edition I choose? I would think choosing Starter would give me the most basic settings, which would apply to all other editions, but I'm not entirely sure of this. I don't intend to install any extra applications or drivers. I merely want to insert an OEM disk, my OPK USB drive, and have it work for whatever edition of Windows 7 I'm installing. If a large number of similarly-configured PCs need to be built, I'll go ahead and create a custom answer file in that case, but for a single machine order, that seems like overkill. In addition, do I need a separate answer file for 32-bit and 64-bit versions of Windows 7? Or will it work for both, even though I copied the Install.wim file from the 32-bit disk? Thanks!

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• SQL Server 2005 standard filegroups / files for performance on SAN

  - by Blootac

  I submitted this to stack overflow (here) but realised it should really be on serverfault. so apologies for the incorrect and duplicate posting: Ok so I've just been on a SQL Server course and we discussed the usage scenarios of multiple filegroups and files when in use over local RAID and local disks but we didn't touch SAN scenarios so my question is as follows; I currently have a 250 gig database running on SQL Server 2005 where some tables have a huge number of writes and others are fairly static. The database and all objects reside in a single file group with a single data file. The log file is also on the same volume. My interpretation is that separate data files should be used across different disks to lessen disk contention and that file groups should be used for partitioning of data. However, with a SAN you obviously don't really have the same issue of disk contention that you do with a small RAID setup (or at least we don't at the moment), and standard edition doesn't support partitioning. So in order to improve parallelism what should I do? My understanding of various Microsoft publications is that if I increase the number of data files, separate threads can act across each file separately. Which leads me to the question how many files should I have. One per core? Should I be putting tables and indexes with high levels of activity in separate file groups, each with the same number of data files as we have cores? Thank you

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• What do different patterns mean in Windows 8 file copy dialog

  - by MainMa

  When copying or extracting files, Windows 8 shows the chart with the speed of the operation. I noticed several patterns: Randomness, High speed at the beginning, then low speed during the most part of the operation, Mostly constant speed. 1. Randomness/nice mountains. 2. High speed at the beginning, then low speed during the most part of the operation. 3. Low speed at the beginning, then high speed during the most part of the operation. (Similar to the previous image, but inverted) 3. Mostly constant speed. (Same as previous image, but without the fast start) I'm curious, what each of those patterns mean? Do some indicate that there may be a problem with hard disk performance? Why the nearly constant speed is so rare, even when copying a single large file from and to a spinning drive, or when copying a single large file or a bunch of small files from and to an SSD?

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• Is it ever good to share a userid?

  - by Ladlestein

  On Un*x, Is it ever a good idea to have one userid that many different people log into when they do stuff? Often I'm installing software or something on a Linux or BSD system. I've developed software for 24 years now, so I know how to make the machine do what I want, but I've never had responsibility for maintaining a multi-user installation where anyone really cared about security. So my opinions feel untested. Now I'm at a company where there's a server that many people log into with a single userid and do stuff. I'm installing some software on it. It's not really a public-facing server, and is only accessible via VPN, but it's used by many people nonetheless, to run tests on custom software, things like that. It's a staging server. I'm thinking that at the very least, using a single user obscures an audit trail, and that's bad. And it's just inelegant, because people don't have their own spaces on the server. But then again, with more userids, maybe there's a greater chance that one can be compromised, allowing attackers to gain access. ?

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• 32 core (each physical core) 2.2 GhZ or 12 core (6 physical cores) 3.0GHZ?

  - by Tejaswi Rana

  I am working on a multithreaded application (Forex trading app built on C#) and had the client upgrade from the 12 core 3.0GHZ machine (Intel) to a 32 core 2.2 Ghz machine (AMD). The PassMark benchmark results were significantly higher when using multicores doing Integer, Floating and other calculations while for a single core calculation it was a bit slower than the pack (others that were being compared to with similar config as the 12 core one). Oh it also comes with 64 GB RAM (4 times as the other one) and a much faster SSD. So after configuring and running the application on that machine, not only did it not perform as well, it was significantly slower. We're talking about 30seconds - 1 minute slower on an app that usually completes processing within 5-20 secs. The application uses MAX DEGREE of PARALLELISM (TPL) which I've tried setting to number of cores and also half of that. I've also tried running single threaded and without setting any limits in parallel threading. While it may be the hardware has some issues, I am wondering if the CPU processing speed is the issue. I can overclock to 3.0 GHZ. But is that even a good idea? Server Info - AMD http://www.passmark.com/forum/showthread.php?4013-AMD-Dual-6272-performance-is-60-lower-than-benchmarks Seems that benchmark was wrong to start with - officially. Intel i7 3930k OS (same in both) Windows 7 Professional 64-bit

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• VPN Trunk Between Cisco ASA 5520 and DrayTek Vigor 2930

  - by David Heggie

  I'm a bit of a VPN newbie, so please go easy on me ... I'm trying to use the VPN trunking capabilities of the DrayTek Vigor 2930 firewall to bond two IPSec VPN connections to a Cisco ASA 5520 device and I'm getting myself tied in knots and hope someone here with more knowledge / experience can help. I have a remote site with two ADSL connections and the DrayTek box. The main office site has the Cisco ASA device. I am able to setup a single IPSec connection between the two sites on either of the ADSL connections' public IP addresses, but as soon as I try to use the VPN bonding, nothing works. The VPN tunnels are both still up, but the traffic is getting lost somewhere. I suspect it's due to the ASA not knowing how to route the traffic back over the VPN - one minute, traffic from my remote office's network is coming from public ip address #1, the next it's coming from public address #2 and it doesn't know what to do. Well, that's my newbie impression of what's going wrong, but I don't really know: If this is really what's happening If what I'm trying to do (bond two VPN connections from a single remote network to improve the bandwidth / resiliency) is possible with the kit I've got Could anyone help?

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• OSX root user keeps re-enabling itself on reboot

  - by geodave

  Running Snow Leopard. Completely inexplicably, I seem to have enabled the OSX root user by accident. I honestly have no idea how it happened, but if memory serves I was looking at the login pane (with my two user accounts) when I must have hit something, and suddenly the two accounts were replaced by one that just said "Other..." Clicking the "Other..." account allows me to type a username and password, but neither of the normal two accounts would work. Since I never set a root password, it wouldn't let me in that way either. So I booted into Single User mode and ran these commands: /sbin/mount -uw / fsck -fy launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist dscl . -passwd /Users/root newpassword and that let me login as root. Then, I went to System Preferences, Accounts, Login Options, clicked Join, Open Directory Utility, and lastly in the Edit menu I clicked "Disable Root User" Great, I thought, back to normal. Except rebooting, I still only have the Other... account visible, and the root password I set beforehand doesn't work anymore! I have to reboot into Single User Mode and go through the whole process again just to get back into the system (as root) How on Earth did I accidentally enable this? I didn't even know about the Directory Utility before now. And most importantly, why the heck would it be re-enabling the root user on boot? Thanks in advance to any help!

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• Is basing storage requirements based on IOPS sufficient?

  - by Boden

  The current system in question is running SBS 2003, and is going to be migrated on new hardware to SBS 2008. Currently I'm seeing on average 200-300 disk transfers per second total across all the arrays in the system. The array seeing the bulk of activity is a 6 disk 7200RPM RAID 6 and it struggles to keep up during high traffic times (idle time often only 10-20%; response times peaking 20-50+ ms). Based on some rough calculations this makes sense (avg ~245 IOPS on this array at 70/30 read to write ratio). I'm considering using a much simpler disk configuration using a single RAID 10 array of 10K disks. Using the same parameters for my calculations above, I'm getting 583 average random IOPS / sec. Granted SBS 2008 is not the same beast as 2003, but I'd like to make the assumption that it'll be similar in terms of disk performance, if not better (Exchange 2007 is easier on the disk and there's no ISA server). Am I correct in believing that the proposed system will be sufficient in terms of performance, or am I missing something? I've read so much about recommended disk configurations for various products like Exchange, and they often mention things like dedicating spindles to logs, etc. I understand the reasoning behind this, but if I've got more than enough random I/O overhead, does it really matter? I've always at the very least had separate spindles for the OS, but I could really reduce cost and complexity if I just had a single, good performing array. So as not to make you guys do my job for me, the generic version of this question is: if I have a projected IOPS figure for a new system, is it sufficient to use this value alone to spec the storage, ignoring "best practice" configurations? (given similar technology, not going from DAS to SAN or anything)

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• How can I manage AWS VPC ssh access accounts and keys across multiple instances?

  - by deitch

  I am setting up a standard AWS VPC structure: a public subnet some private subnets, hosts on each, ELB, etc. Operational network access will be via either an ssh bastion host or an openvpn instance. Once on the network (bastion or openvpn), admins use ssh to access the individual instances. From what I can tell all of the docs seem to depend on a single user with sudo rights and a single public ssh key. But is that really best practice? Isn't it much better to have each user access each host under their own name? So I can deploy accounts and ssh public keys to each server, but that rapidly gets unmanageable. How do people recommend managing user accounts? I've looked at: IAM: It doesn't like like IAM has a method for automatically distributing accounts and ssh keys to VPC instances. IAM via LDAP: IAM doesn't have an LDAP API LDAP: set up my own LDAP servers (redundant, of course). Bit of a pain to manage, still better than managing on every host, especially as we grow. Shared ssh key: rely on the VPN/bastion to track user activities. I don't love it, but... What do people recommend? NOTE: I moved this over from accidentally posting in StackOverflow.

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• Copying email with qmail and Plesk

  - by Greg

  I need to keep a copy of all outgoing and incoming email (for a single domain if possible) using qmail or Plesk. I can't recompile qmail, so qmailtap is out of the question, as is setting QUEUE_EXTRA in extra.h. I'm pretty sure it should be possible with Plesk's mailmng utility, aka Mail Handlers but I'm having trouble getting them to work. I've registered 2 hooks: incoming hook ./mailmng --add-handler --handler-name=incoming --recipient-domain=example.com --executable=/xxx/incoming.sh --context=/xxx/incoming/ --hook=before-local incoming.sh #!/bin/bash # The email is passed on stdin - grab it to a variable e=`cat -` # $1 = context (/xxx/incoming) # $3 = recipient ([email protected]) # Create /xxx/incoming/[email protected] mkdir -p $1$3 # Save the email to /xxx/incoming/[email protected]/0123456789.txt echo "$e" > $1$3/`date +%s%N`.txt # Echo PASS to stderr echo 'PASS' >&2 # Echo the email to stdout echo "$e" outgoing hook # ./mailmng --add-handler --handler-name=outgoing --sender-domain=holidaysplease.com --executable=/xxx/outgoing.sh --context=/xxx/outgoing/ --hook=before-remote The outgoing.sh file is the same as incoming.sh, except replace $3 (recipient) with $2 (sender). The incoming hook does work, but saves 2 copies of each email - one before and one after SpamAssassin has run. The outgoing hook doesn't seem to get called at all. So finally, my questions are: How can I make the incoming hook save only a single copy (preferably after SpamAssassin has run)? How can I get the outgoing hook to work?

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• Deploying workstations - best practices?

  - by V. Romanov

  Hi guys I've been researching on the subject of workstation deployment for a while, and found a ton of info and dozens different methods and tools, but no "best practice" method that doesn't lack at least one feature that i consider required for the solution to be perfect. I'm currently interested in windows workstation deployment, but if the tools can be extended to Linux, then it's an added value. I want the deployment tools I use to be able to do the following: hardware independent - I want my image or installation to have a minimum of hardware and driver dependency, so that i can use a single image/package for all workstations easily updatable - I want to be able to update my image as easily as possible without redeploying/rebuilding/reimaging all configurations PXE bootable deployment - I want the tools to be bootable off the network so that I don't need a boot cd/DOK. scriptable for minimum human input - Ideally, the tool should run automatically after being booted and perform a "default" deployment (including partitioning) unless prompted otherwise. i.e - take a pc, hook it up, power on, PXE boot and forget about it until the OS is deployed. I found no single product or environment that does all this. Closest i came to is the windows deployment services/WIM image format. I also checked out numerous imaging and deployment tools including clonezilla, ghost, g4u, wpkg and others, but most of them lack the hardware Independence and updatability features. We currently have a Symantec Ghost server setup that does imaging over the network, but I'm not satisfied with it as it has all the drawbacks i listed above. Do you have suggestions how to optimize the process of workstation deployment? How do you deploy them in your organization? Thanks! Vadim.

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• cpu load measure with hyperthreading on linux

  - by dronus

  How can I get the true usage of a multicore hyperthreading enabled cpu? For example lets consider a 2 core CPU, expressing 4 virtual cores. A single threaded workload would now show up as 100% in top, as one core of the virtual cores is completely used. The CPU and top work as expected, like there would be 4 real cores. With two threads however, the things get arkward: If all works well, they are balanced to the two real cores, so we got 200% usage: Two times 100% and two idle virtual cores, and are using all of the available CPU power. Seems ok to me. However, if the two threads would run on a single real core, they would show up as using two times 100%, that makes 200% virtual core usage. But on the real side, that would be one core sharing its power on the two threads, which are then using only one half of the total CPU power. So the usage numbers shown by top can not be used to measure the total CPU workload. I also wonder how hyperthreading balances two virtual on a real core. If two threads take a different amount of cycles, would the virtual cores 'adapt' so that both show a 100% load even if the real load differ?

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• I/O APIC on Virtualbox

  - by RidDeBakTiYar

  I'm trying to use the PIT to do APIC timer calibration, and I want to use the PIT through I/O APIC instead of PIC. On Bochs I get interrupts from the PIT at the asked frequency from the I/O APIC, while on Virtualbox I can't receive a single interrupt. It must be an I/O APIC configuration problem because as I unmask the first PIC entry, the IRQ fires. However that's not what I want. Can you imagine any possible condition that wouldn't make Virtualbox fire the IRQ? I'm not assuming single I/O APIC configuration (even though Virtualbox has only 1). I'm not assuming identity mappings between ISA IRQs and I/O APIC GSIs (using ACPI MADT table to get I/O APIC base address and Int override). I'm setting the Trigger Mode and Polarity bits correctly (on Virtualbox they are set as '00 - default' which means edge high right?). I'm putting the BSP APIC ID into the Destination field (using Physical destination) and vector 0x20. Being the BSP APIC ID 0 on Virtualbox, it ends up with 0x0000000000000020 written to the IOREDTBL. And, just in case I'm getting the wrong values from the Interrupt Override descriptor, I'm setting this value to all the IOREDTBL entries (I know this is very very bad, and it wont be kept as I understand what's going on). The only thing I didn't check out is Local APIC configuration. Actually I'm not writing any value to the BSP LAPIC. Just reading the APIC ID and using it to boot APs through IPIs. And obviously I'm setting bit 11 in the IA32_APIC_BASE MSR to enable the LAPIC. Any ideas? Thanks in advance.

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• Performance Test and TCP tuning

  - by Mithir

  We are in the process of performance testing an application which receives tcp requests converts them to soap requests (WCF-httpBinding) which other services work on. The server is Windows Server 2008 R2. The TCP requests are received by TcpListener instance (.NET C#). There are 3 http-binded WCF services running on the same server. We have built a performance test client which goal is to simulate multiple concurrent requests(each request has to be different and recognizable by the application). We built a test running 150 requests that run on the same time (by 150 different threads), and we noticed straight away that some requests get the TCP connection slowly, but once they get it, they act fast. A single request writes twice on the same connection- request and an application ack. Although a single request+ack can take about 150ms, the 150 test takes about 7 seconds. The Problem When we try to run this test from 2 different computers we lose requests. some clients requests are getting no connection was made because the target machine actively refused it So I got here and got convinced it was because of the backlog. I changed the TcpListener parameters and did the registry AFD backlog changes written here but it still didn't work, so I inserted all of the TCP tuning suggested plus some netsh commands which were recommended, but still no change, we still get that error. Is there anything else I need to know? Are there any other solutions?

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• Backup software for incremental swapped-out drives?

  - by user13743

  We're using Acronis Home 11 to backup our main Windows machine at the office. We have a set of portable hard drives that we swap out each week, for redundancy. We have incremental sets ( a new diff of the entire series each night) building on each drive. However, from time to time, Acronis gets confused and sometimes makes a new full backup. This eats up a lot of drive on the disks. Also, I have to trick the Acronis script each time I swap out a drive and point it to the new incremental backup set. Finally, if a drive gets full, there's no way to partition the backup set on a drive. I found this out the hard way, and now one drive is full with one backup set. So now on the other drive, I have three folders of backup sets. When one starts to get full, I delete the oldest one and start a new set. That way one single drive never gets filled up with one single backup set. I'm looking for a backup software that can backup Windows in incremental sets, and doesn't get tripped up with swapped out drives. Is there a better solution?

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• Formula to calculate probability of unrecoverable read error during RAID rebuild

  - by OlafM

  I need to compare the reliability of different RAID systems with either consumer or enterprise drives. The formula to have the probability of success of a rebuild, ignoring mechanical problems, is simple: error_probability = 1 - (1-per_bit_error_rate)^bit_read and with 3 TB drives I get 38% probability to experience an URE (unrecoverable read error) for a 2+1 disks RAID5 (4.7% for enterprise drives) 21% for a RAID1 (2.4% for enterprise drives) 51% probability of error during recovery for the 3+1 RAID5 often used by users of SOHO products like Synologys. Most people don't know about this. Calculating the error for single disk tolerance is easy, my question concerns systems tolerant to multiple disks failures (RAID6/Z2, RAIDZ3 and RAID1 with multiple disks). If only the first disk is used for rebuild and the second one is read again from the beginning in case or an URE, then the error probability is the one calculated above squared (14.5% for consumer RAID5 2+1, 4.5% for consumer RAID1 1+2). However, I suppose (at least in ZFS that has full checksums!) that the second parity/available disk is read only where needed, meaning that only few sectors are needed: how many UREs can possibly happen in the first disk? not many, otherwise the error probability for single-disk tolerance systems would skyrocket even more than I calculated. If I'm correct, a second parity disk would practically lower the risk to extremely low values. Am I correct?

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• SQL Server 2005 standard filegroups / files for performance on SAN

  - by Blootac

  Ok so I've just been on a SQL Server course and we discussed the usage scenarios of multiple filegroups and files when in use over local RAID and local disks but we didn't touch SAN scenarios so my question is as follows; I currently have a 250 gig database running on SQL Server 2005 where some tables have a huge number of writes and others are fairly static. The database and all objects reside in a single file group with a single data file. The log file is also on the same volume. My interpretation is that separate data files should be used across different disks to lessen disk contention and that file groups should be used for partitioning of data. However, with a SAN you obviously don't really have the same issue of disk contention that you do with a small RAID setup (or at least we don't at the moment), and standard edition doesn't support partitioning. So in order to improve parallelism what should I do? My understanding of various Microsoft publications is that if I increase the number of data files, separate threads can act across each file separately. Which leads me to the question how many files should I have. One per core? Should I be putting tables and indexes with high levels of activity in separate file groups, each with the same number of data files as we have cores? Thank you

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• Load Sharing Regarding Large Websites

  - by JHarley1

  Hello, I have a question regarding Load Sharing for large websites. My Understanding: So if you have a website that has millions of fits a day you will need to have an architecture that can support this sort of pressure. You can either do one or two things: Invest in a single large server that has huge amounts of processing power, memory and storage (such as Microsoft's TerraServer). Spread the load of your website across a number of machines. Let me tackle the second approach, so you have a collection of machines all running Web Server Software and all having access to identical copies of the websites pages. You can either spread the load across these machines using a cyclic pattern in a DNS or you can use a Load Ballancing Switch. The advantages of this approach is: - Redundancy - servers can fail and the others would "pick up the slack" - Incremental - the ability to easily add new machines to this set-up. My Question's Is there a Virtual approach to this issue of load balancing now? If the website runs from a database - is there still only a single copy of the database? If a user had a session running on one Server (e.g. they had gone to www.example.org and had been assigned to Server 2 - were they had created a session) if they refreshed the website (and were allocated Server 3) would they still have their session? What are the other disadvantages associated with Load Balancing? Many Thanks, J

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• Loop through several servers, find specific dlls , get the dll version, internal filename and path?

  - by Graham

  I am a newby to Powershell, and using PS v2. I can see the massive potential it has, but I just can't get the following code to work fully. I am trying to end up with a csv file that contains the wild carded required dlls in the GAC_MSIL or sub-directory, get the dll version, internal filename and path, and the server IP address. The code is below, and it is in single line format because it appears easier to remote onto one of the servers in the server farm and run the single line from that console, ue to security log-ins etc. The code has produced a set of results, but only for the last server, it probably does the first server, then overwrites it but I am not sure about that. I have done a lot of reading about using arrays, and custom objects, and had a go at doing that, but my scripting skills in PS are not yet up to it. Code: $out = "Ouput_dll_ver_results.csv";foreach ($server in '11.222.33.123', '11.222.33.124') {$VersionInfo = (Get-ChildItem \$server\C$\windows\assembly\GAC_MSIL -recurse -Include abc*.dll,def*.dll,ghi*.dll,jkl*.dll | Where-Object { $.FullName -notmatch "\windows\assembly\temp\" })}; $VersionInfo | %{Get-Command $.FullName} | select -expand File* |Export-Csv $out Can you please advise if/how the above code can be corrected, and if not, what alternatives do I have to get the information I need. Many thanks in advance. Graham

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