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  • AFP, SMB, NFS which is the best data transfer protocol ?

    - by Kami
    I have a computer with large hard disks running Gentoo. I have to serve med/big files via a wired network to Apple devices (all of them running OS X). Which protocol is the best for the following needs ? : Speed Ease of use (by the clients and the server) Less limited (max file size, limited charset for filenames) Security

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  • Just to not to be ingnorant.

    - by atch
    Could anyone explain to me why is it that producers of processors claim that their processor can perform so many thousands (or millions) operations per second and yet typical program (Word, VS etc.) on my machine with 4GB, 3500hz starts with no less than 10sek. Have to mention that I've just formatted disk and tick any necessarry boxes to optimize my machine. So if for example outlook starts in 10 sek I wonder how many millions of operations have to be performed to run such program? Thanks

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  • Why might apache2 use 100% of CPU at startup?

    - by QuantumMechanic
    This is apache 2.2.14 on SLES9. Out of nowhere (i.e. it had been working fine for ages) I am seeing apache2 suddenly start using 100% of the CPU at startup, and never completing startup. Nothing is getting written to /var/log/error_log (when it did back when things were OK). ps only shows the main httpd process and not any of the spawned threads. When things were OK, it would show the spawned threads. So it appears httpd is going into some sort of infinite loop right at startup and isn't even completing startup. It's not an issue of being overloaded by connections -- this happens even when nothing is trying to contact it. The config files haven't changed (or at least they haven't changed in a way that changed their last-modified time). I've tried added -e debug -E /var/log/apache2/startup_info to the command line, but nothing is put in the file. Any ideas what could be happening?

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  • Simple tool to graph memory usage?

    - by dbr
    Is there a script that will show memory usage as a graph, for example as a pie-chart, with each process being being a separate slice? I'm not looking for something like Munin to graph memory usage over time, but rather show the memory usage per-process at a single point in time. To make my request even more obscure, it is for a headless server (so no X applications). The simplest way would be to write a PNG file, or possibly an HTML file (which could use Javascript to allow the filtering of processes, changing between graph-types and so on)

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  • Running a VM off a USB 2.0 Flash Drive - Mac/Parallels/XP

    - by geerlingguy
    I use a MacBook Air as my primary machine, and the 128GB SSD means space is precious. To save about 10 GB, I've been running Parallels with a Windows XP VM off an external USB hard drive, which performs as well in everyday use as running the VM off the internal SSD. So, I bought a tiny 32GB USB 2.0 flash drive, plugged it into the MacBook Air, formatted it first as ExFAT (which was slow), then as Mac OS Extended (Journaled) (which was also slow), and copied over my VM file, and ran Parallels off it. My full experience is documented here: http://www.midwesternmac.com/blogs/jeff-geerling/running-windows-xp-vm Straight file copies are really fast — 30 MB/sec read (solid the whole time), and 10-11 MB/sec write (solid the whole time). But I noticed that once XP started running, the disk access rates were in the low KB ranges. Are USB flash drives really that poor at random access, or could I possibly be missing something (the format of the flash drive, etc.?)? Of note, I've tried the following, to no great effect: Formatting the drive as either ExFAT or Mac OS Extended (Journaled) Unplugging all other USB devices and turning off Bluetooth (which runs on the right-side-port USB bus). Plugging in the flash drive either direct in the right side port, or the left side port, or into a USB 2.0 hub

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  • Cause of slow download speed on a particular EC2 instance?

    - by James
    I have a networking issue I'm trying to solve. I have two EC2 instances, same zone, same type. On one of the two EC2 instances (the 'bad' instance), the download speed is really poor (200k/s), while on the other (the 'good' instance), the download speed is fine, comfortable at 30M/s +). To clarify, I'm talking about downloading files to the EC2 instance while ssh'd into the server, e.g running wget with a large file. I've tried different files, including S3 objects and a large linux ISO from elsewhere. Running ethtool eth0 only returns 'Link detected: yes' for both. When running ifconfig, both return the same for most part, aside from how the good instance shows no error packets yet the bad instance shows many: UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:168372370 errors:5075643 dropped:0 overruns:0 frame:0 TX packets:122116480 errors:0 dropped:0 overruns:0 carrier:0 Both servers are configured the same, at least were supposed to be. How can I go about diagnosing the cause for the slow download speed? Is there anything particular to EC2 instances that could cause this? Having trouble knowing where to start. Thanks for any help!

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  • limit linux background flush (dirty pages)

    - by korkman
    Background flushing in linux happens when either too much written data is pending (adjustable via /proc/sys/vm/dirty_background_ratio) or a timeout for pending writes is reached (/proc/sys/vm/dirty_expire_centisecs). Unless another limit is being hit (/proc/sys/vm/dirty_ratio), more written data may be cached. Further writes will block. In theory, this should create a background process writing out dirty pages without disturbing other processes. In practice, it does disturb any process doing uncached reading or synchronous writing. Badly. This is because the background flush actually writes at 100% device speed and any other device requests at this time will be delayed (because all queues and write-caches on the road are filled). Is there any way to limit the amount of requests per second the flushing process performs, or otherwise effectively prioritize other device I/O?

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  • Building optimal custom machine for Sql Server

    - by Chad Grant
    Getting the hardware in the mail any day. Hardware related to my question: x10 15.5k RPM SAS Segate Cheetah's x2 Adaptec 5405 PCIe Raid cards Motherboard has integrated SAS raid. Was thinking I would build 2 RAID 10 arrays one for data and one for logs The remaining 2 drives a RAID 0 for TempDB Will probably throw in a drive for OS. Does putting the Sql Server application / exe's on a raid make a difference and is there any impact of leaving the OS on a relatively slow disk compared to the raid arrays? I have 5/6 DBs combined < 50 gigs. With a relatively good / constant load. Estimating 60-7% reads vs writes. Planning on using log shipping as well if that matters. Any advice or suggestions?

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  • One network, two macbooks, one is fast and the other is slow

    - by Brendan
    I really need help for my friend. I know next to nothing about computers. My roommate and I both have macbook pros from the same year running OS X, are both connecting wirelessly to the same xfinity wifi, and while mine runs perfectly fine, my roommate complains that his works very slowly and times out every few seconds. I can't seem to figure out why this is. He is trying to get me to switch internet providers because he is convinced that it is their problem, but this cannot possibly be the issue since it works great on mine. He has an xbox hooked up to the wifi that he says also works poorly. I really can't see switching providers given that I am experiencing absolutely zero problems. How can I help my friend?

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  • Samba PDC share slow with LDAP backend

    - by hmart
    The scenario I have a SUSE SLES 11.1 SP1 machine as Samba master PDC with LDAP backend. In one share there are Database files for a Client-Server application. I log XP and Windows 7 machines to the local domain (example.local), the login is a little slow but works. In the client computers have an executable which opens, reads and writes the database files from the server share. The Problem When running Samba with LDAP password backend the client application runs VERY SLOW with a maximum transfer rate of 2500 MBit per second. If disable LDAP the client app speed increases 20x, with transfer rate of 50Mbit/sec and running smoothly. I'm doing test with just two users and two machines, so concurrency, or LDAP size shouldn't be the problem here. The suspect LDAP, Smb.conf [global] section configuration. The Question What can I do? I've googled a lot, but still have no answer. Slow smb.conf WITH LDAP [global] workgroup = zmartsoft.local passdb backend = ldapsam:ldap://127.0.0.1 printing = cups printcap name = cups printcap cache time = 750 cups options = raw map to guest = Bad User logon path = \\%L\profiles\.msprofile logon home = \\%L\%U\.9xprofile logon drive = P: usershare allow guests = Yes add machine script = /usr/sbin/useradd -c Machine -d /var/lib/nobody -s /bin/false %m$ domain logons = Yes domain master = Yes local master = Yes netbios name = server os level = 65 preferred master = Yes security = user wins support = Yes idmap backend = ldap:ldap://127.0.0.1 ldap admin dn = cn=Administrator,dc=zmartsoft,dc=local ldap group suffix = ou=Groups ldap idmap suffix = ou=Idmap ldap machine suffix = ou=Machines ldap passwd sync = Yes ldap ssl = Off ldap suffix = dc=zmartsoft,dc=local ldap user suffix = ou=Users

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  • MySQL: Load database to memory

    - by Adam Matan
    Hi, Is there a way to load an entire MySQL database to the RAM, especially on en EC2 server? The database is quite small (~500 MegaBytes) I have enough memory Speed issues are crucial - the resulted queries are used to serve a dynamic webpage. Thanks, Adam

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  • Does this prove a network bandwidth bottleneck?

    - by Yuji Tomita
    I've incorrectly assumed that my internal AB testing means my server can handle 1k concurrency @3k hits per second. My theory at at the moment is that the network is the bottleneck. The server can't send enough data fast enough. External testing from blitz.io at 1k concurrency shows my hits/s capping off at 180, with pages taking longer and longer to respond as the server is only able to return 180 per second. I've served a blank file from nginx and benched it: it scales 1:1 with concurrency. Now to rule out IO / memcached bottlenecks (nginx normally pulls from memcached), I serve up a static version of the cached page from the filesystem. The results are very similar to my original test; I'm capped at around 180 RPS. Splitting the HTML page in half gives me double the RPS, so it's definitely limited by the size of the page. If I internally ApacheBench from the local server, I get consistent results of around 4k RPS on both the Full Page and the Half Page, at high transfer rates. Transfer rate: 62586.14 [Kbytes/sec] received If I AB from an external server, I get around 180RPS - same as the blitz.io results. How do I know it's not intentional throttling? If I benchmark from multiple external servers, all results become poor which leads me to believe the problem is in MY servers outbound traffic, not a download speed issue with my benchmarking servers / blitz.io. So I'm back to my conclusion that my server can't send data fast enough. Am I right? Are there other ways to interpret this data? Is the solution/optimization to set up multiple servers + load balancing that can each serve 180 hits per second? I'm quite new to server optimization, so I'd appreciate any confirmation interpreting this data. Outbound traffic Here's more information about the outbound bandwidth: The network graph shows a maximum output of 16 Mb/s: 16 megabits per second. Doesn't sound like much at all. Due to a suggestion about throttling, I looked into this and found that linode has a 50mbps cap (which I'm not even close to hitting, apparently). I had it raised to 100mbps. Since linode caps my traffic, and I'm not even hitting it, does this mean that my server should indeed be capable of outputting up to 100mbps but is limited by some other internal bottleneck? I just don't understand how networks at this large of a scale work; can they literally send data as fast as they can read from the HDD? Is the network pipe that big? In conclusion 1: Based on the above, I'm thinking I can definitely raise my 180RPS by adding an nginx load balancer on top of a multi nginx server setup at exactly 180RPS per server behind the LB. 2: If linode has a 50/100mbit limit that I'm not hitting at all, there must be something I can do to hit that limit with my single server setup. If I can read / transmit data fast enough locally, and linode even bothers to have a 50mbit/100mbit cap, there must be an internal bottleneck that's not allowing me to hit those caps that I'm not sure how to detect. Correct? I realize the question is huge and vague now, but I'm not sure how to condense it. Any input is appreciated on any conclusion I've made.

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  • How to diagnose very slow pagefile

    - by svick
    Quite often, one of the applications I use freezes (“does not respond”) for a while, in extreme cases for few minutes. This happens especially when when switching apps. During this time, the HDD light flashes constantly and perfmon show that HDD is used 100% of the time (OTOH, CPU isn't) and that pagefile is being read (which is to be expected when switching apps), but at a very slow rate. When I sort the disk table in perfmon by read or write, the file read and wrote the most is the pagefile, but it's still quite low rate (I don't remember the numbers). How can I diagnose what's causing this? I use Windows Vista, and the computer is quite ordinary two years old laptop.

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  • Which is faster for read access on EC2; local drive or EBS?

    - by Phillip Oldham
    Which is faster for read access on an EC2 instance; the "local" drive or an attached EBS volume? I have some data that needs to be persisted so have placed this on an EBS volume. I'm using OpenSolaris, so this volume has been attached as a ZFS pool. However, I have a large chunk of EC2 disk space that's going to go unused, so I'm considering re-purposing this as a ZFS cache volume but I don't want to do this if the disk access is going to be slower than that of the EBS volume as it would potentially have a detrimental effect.

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  • nginx+php-fpm help optimize configs

    - by Dmitro
    I have 3 servers. First server (CPU - model name: 06/17, 2.66GHz, 4 cores, 8GB RAM) have nginx as load balancer with next config upstream lb_mydomain { server mydomain.ru:81 weight=2; server 66.0.0.18 weight=6; } server { listen 80; server_name ~(?!mydomain.ru)(.*); client_max_body_size 20m; location / { proxy_pass http://lb_mydomain; proxy_redirect off; proxy_set_header Connection close; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_pass_header Set-Cookie; proxy_pass_header P3P; proxy_pass_header Content-Type; proxy_pass_header Content-Disposition; proxy_pass_header Content-Length; } } And configs from nginx.conf: user www-data; worker_processes 5; # worker_priority -1; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; events { worker_connections 5024; # multi_accept on; } http { include /etc/nginx/mime.types; access_log /var/log/nginx/access.log; sendfile on; default_type application/octet-stream; #tcp_nopush on; keepalive_timeout 65; tcp_nodelay on; gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; # PHP-FPM (backend) upstream php-fpm { server 127.0.0.1:9000; } include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } And config php-fpm: listen = 127.0.0.1:9000 ;listen.backlog = -1 ;listen.allowed_clients = 127.0.0.1 ;listen.owner = www-data ;listen.group = www-data ;listen.mode = 0666 user = www-data group = www-data pm = dynamic pm.max_children = 80 ;pm.start_servers = 20 pm.min_spare_servers = 5 pm.max_spare_servers = 35 ;pm.max_requests = 500 pm.status_path = /status ping.path = /ping ;ping.response = pong request_terminate_timeout = 30s request_slowlog_timeout = 10s slowlog = /var/log/php-fpm.log.slow ;rlimit_files = 1024 ;rlimit_core = 0 ;chroot = chdir = /var/www ;catch_workers_output = yes ;env[HOSTNAME] = $HOSTNAME ;env[PATH] = /usr/local/bin:/usr/bin:/bin ;env[TMP] = /tmp ;env[TMPDIR] = /tmp ;env[TEMP] = /tmp ;php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i -f [email protected] ;php_flag[display_errors] = off ;php_admin_value[error_log] = /var/log/fpm-php.www.log ;php_admin_flag[log_errors] = on ;php_admin_value[memory_limit] = 32M In top I see 20 php-fpm processes which use from 1% - 15% CPU. So it's have high load averadge: top - 15:36:22 up 34 days, 20:54, 1 user, load average: 5.98, 7.75, 8.78 Tasks: 218 total, 1 running, 217 sleeping, 0 stopped, 0 zombie Cpu(s): 34.1%us, 3.2%sy, 0.0%ni, 37.0%id, 24.8%wa, 0.0%hi, 0.9%si, 0.0%st Mem: 8183228k total, 7538584k used, 644644k free, 351136k buffers Swap: 9936892k total, 14636k used, 9922256k free, 990540k cached Second server(CPU - model name: Intel(R) Xeon(R) CPU E5504 @ 2.00GHz, 8 cores, 8GB RAM). Nginx configs from nginx.conf: user www-data; worker_processes 5; # worker_priority -1; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; events { worker_connections 5024; # multi_accept on; } http { include /etc/nginx/mime.types; access_log /var/log/nginx/access.log; sendfile on; default_type application/octet-stream; #tcp_nopush on; keepalive_timeout 65; tcp_nodelay on; gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; # PHP-FPM (backend) upstream php-fpm { server 127.0.0.1:9000; } include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } And config of php-fpm: listen = 127.0.0.1:9000 ;listen.backlog = -1 ;listen.allowed_clients = 127.0.0.1 ;listen.owner = www-data ;listen.group = www-data ;listen.mode = 0666 user = www-data group = www-data pm = dynamic pm.max_children = 50 ;pm.start_servers = 20 pm.min_spare_servers = 5 pm.max_spare_servers = 35 ;pm.max_requests = 500 ;pm.status_path = /status ;ping.path = /ping ;ping.response = pong ;request_terminate_timeout = 0 ;request_slowlog_timeout = 0 ;slowlog = /var/log/php-fpm.log.slow ;rlimit_files = 1024 ;rlimit_core = 0 ;chroot = chdir = /var/www ;catch_workers_output = yes ;env[HOSTNAME] = $HOSTNAME ;env[PATH] = /usr/local/bin:/usr/bin:/bin ;env[TMP] = /tmp ;env[TMPDIR] = /tmp ;env[TEMP] = /tmp ;php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i -f [email protected] ;php_flag[display_errors] = off ;php_admin_value[error_log] = /var/log/fpm-php.www.log ;php_admin_flag[log_errors] = on ;php_admin_value[memory_limit] = 32M In top I see 50 php-fpm processes which use from 10% - 25% CPU. So it's have high load averadge: top - 15:53:05 up 33 days, 1:15, 1 user, load average: 41.35, 40.28, 39.61 Tasks: 239 total, 40 running, 199 sleeping, 0 stopped, 0 zombie Cpu(s): 96.5%us, 3.1%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.4%si, 0.0%st Mem: 8185560k total, 7804224k used, 381336k free, 161648k buffers Swap: 19802108k total, 16k used, 19802092k free, 5068112k cached Third server is server with database postgresql. Also i try ab -n 50 -c 5 http://www.mydomain.ru/ And I get next info: Complete requests: 50 Failed requests: 48 (Connect: 0, Receive: 0, Length: 48, Exceptions: 0) Write errors: 0 Total transferred: 9271367 bytes HTML transferred: 9247767 bytes Requests per second: 1.02 [#/sec] (mean) Time per request: 4882.427 [ms] (mean) Time per request: 976.486 [ms] (mean, across all concurrent requests) Transfer rate: 185.44 [Kbytes/sec] received Please advise how can I make lower level of load average?

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  • Is it reasonable that a random disk seek & read costs ~16ms?

    - by fzhang
    I am frustrated about the latency of random reading from a non-ssd disk. Based on results from following test program, it speeds ~16 ms for a random read of just 512 bytes without help of os cache. I tried changing 512 to larger values, such as 25k, and the latency did not increase as much. I guess it is because the disk seek dominates the time. I understand that random reading is inherently slow, but just want to be sure that ~16ms is reasonable, even for non-ssd disk. #include <sys/stat.h> #include <sys/time.h> #include <sys/types.h> #include <sys/unistd.h> #include <fcntl.h> #include <limits.h> #include <stdio.h> #include <string.h> int main(int argc, char** argv) { int fd = open(argv[1], O_RDONLY); if (fd < 0) { fprintf(stderr, "Failed open %s\n", argv[1]); return -1; } const size_t count = 512; const off_t offset = 25990611 / 2; char buffer[count] = { '\0' }; struct timeval start_time; gettimeofday(&start_time, NULL); off_t ret = lseek(fd, offset, SEEK_SET); if (ret != offset) { perror("lseek error"); close(fd); return -1; } ret = read(fd, buffer, count); if (ret != count) { fprintf(stderr, "Failed reading all: %ld\n", ret); close(fd); return -1; } struct timeval end_time; gettimeofday(&end_time, NULL); printf("tv_sec: %ld, tv_usec: %ld\n", end_time.tv_sec - start_time.tv_sec, end_time.tv_usec - start_time.tv_usec); close(fd); return 0; }

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  • Zabbix machine is going crazy with HD writes!

    - by gshankar
    I recently installed Zabbix on a Ubuntu box I had sitting around. It's only monitoring 2 servers but I've noticed that it's continuously smashing the HD with writes. I don't remember Zabbix being this resource heavy when I've used it in the past... Any ideas on why this is happening and what I can do about it? Running iotop gives me this: 1710 be/4 mysql 0.00 B/s 102.12 K/s 0.00 % 0.00 % mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock --port=3306 1723 be/4 mysql 0.00 B/s 0.00 B/s 0.00 % 0.00 % mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld I'm pretty sure it's Zabbix that's causing all that mysql activity as it's the only thing which uses mysql which is running on the box...

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  • Why can't we capture the design of software more effectively?

    - by Ira Baxter
    As engineers, we all "design" artifacts (buildings, programs, circuits, molecules...). That's an activity (design-the-verb) that produces some kind of result (design-the-noun). I think we all agree that design-the-noun is a different entity than the artifact itself. A key activity in the software business (indeed, in any business where the resulting product artifact needs to be enhanced) is to understand the "design (the-noun)". Yet we seem, as a community, to be pretty much complete failures at recording it, as evidenced by the amount of effort people put into rediscovering facts about their code base. Ask somebody to show you the design of their code and see what you get. I think of a design for software as having: An explicit specification for what the software is supposed to do and how well it does it An explicit version of the code (this part is easy, everybody has it) An explanation for how each part of the code serves to achieve the specification A rationale as to why the code is the way it is (e.g., why a particualr choice rather than another) What is NOT a design is a particular perspective on the code. For example [not to pick specifically on] UML diagrams are not designs. Rather, they are properties you can derive from the code, or arguably, properties you wish you could derive from the code. But as a general rule, you can't derive the code from UML. Why is it that after 50+ years of building software, why don't we have regular ways to express this? My personal opinion is that we don't have good ways to express this. Even if we do, most of the community seems so focused on getting "code" that design-the-noun gets lost anyway. (IMHO, until design becomes the purpose of engineering, with the artifact extracted from the design, we're not going to get around this). What have you seen as means for recording designs (in the sense I have described it)? Explicit references to papers would be good. Why do you think specific and general means have not been succesful? How can we change this?

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  • Extracting one file from archive: 7-zip requires decompressing entire archive?

    - by siikamiika
    I've noticed that when browsing an archive containing multiple files with 7-zip 9.20 Windows GUI, extracting one file for previewing takes significantly longer with .7z than .rar archives. With .7zips it also cycles through the filenames in the archive. To me it looks like decompressing the entire archive and keeping just one file. Is there a setting in 7-zip (current or beta/alpha versions) that allows RAR-like behavior?

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  • dd oflag=direct 5x fast

    - by César
    I have Centos 6.2 in server with this specs: 2xCPU 16 Core AMD Opteron 6282 SE 64GB RAM Raid controller H700 1GB cache NV - 2HD 74GB SAS 15Krpm RAID1 stripe 16k (OS Centos 6.2) sda - 4HD 146GB SAS 15Krpm RAID10 stripe 16k (ext4 bs 4096, no barriers) sdb -> /vol01 Raid controller H800 1GB cache nv - MD1200 12HD 300GB SAS 15Krpm RAID10 stripe 256k (For DB Postgres 8.3.18) (ext4 bs 4096, stride 64, stripe-width 384, no barriers) sdc -> /vol02 I'm benchmarking IO speed with dd, and view thah if in RAID10 12 disk exec: dd if=/dev/zero of=DD bs=8M count=10000 oflag=direct 10000+0 records in 10000+0 records out 83886080000 bytes (84 GB) copied, 126,03 s, 666 MB/s but if I remove "oflag=direct" option obtain about 80 MB/s. In read benchmark, results are similar: dd of=/dev/null if=DD bs=8M count=10000 iflag=direct 10000+0 records in 10000+0 records out 83886080000 bytes (84 GB) copied, 79,5918 s, 1,1 GB/s If remove iflag=direct obtain 150MB/s... I don't understand this huge differences, on other machines y don't have this behavior. Can I have some kernel parameter misconfigured? Thanks!

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  • Throughput = BS * IOPS?

    - by Marvin
    I've seen in many places that throughput = bs * iops should be true. For example writing at 128k block size to a SAS disk that can support 190 IOPS should give a throughput of ~23 MBps - 23.75(MBs) = 128(BS)*190(SAS-15 IOPS)/1024. Now when I tested it in a VM against a monster NetApp filer I got theses results: # dd if=/dev/zero of=/tmp/dd.out bs=4k count=2097152 8589934592 bytes (8.6 GB) copied, 61.5996 seconds, 139 MB/s To view the IO rate of the VM I used iostat and esxtop, and they both showed around 250 IOPS. So to my understanding the throughput was supposed to be ~1000k: 1000(KBs) = 4(BS)*250(IOPS). dd of 8GB is twice the size of RAM of course, so no page caching here. What am I missing? Thanks!

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  • How to mirror filesystems with millions of hardlinks?

    - by Thomas Berger
    We have one big problem at the moment: We need to mirror a filesystem for one of our customers. Thats usual not really a problem, but here it is: On this filesystem there is one folder with millions of hardlinks (yes! MILLIONS!). rsync requires more then 4 days to just build the filelist. We use the following rsync options: rsync -Havz --progress serverA:/data/cms /data/ Has anyone a idea how to speed up this rsync, or use alternatives? We could not use dd as the target disk is smaller then the source.

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