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• SQL Server Connectivity Portal

  - by Enrique Lima

  We all love one stop portals :-) Browsing around MSDN I came across this for connectivity, yes, a one stop portal, find info on connecting using a variety of technologies and good guides. http://msdn.microsoft.com/en-us/sqlserver/connectivity.aspx

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• DD-WRT - Where's the best place to get a LinkSys WRT54G V1.0?

  - by Giffyguy

  Looking for the initial release of the LinkSys WRT54G, not V1.1 or V2.0 or anything like that. If it comes with DD-WRT pre-installed, even better. That being said, I suppose a side question would be whether SU recommends different hardware. After all, DD-WRT may have been originally built for the WRT54G and the WRT54Gv1.0 may have better hardware than any of the successive models, but it's still fairly dated. Are there newer routers that are more stable or performant with DD-WRT?

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• How many megabytes per second may I expect from a gigabit USB 2.0 network card under linux?

  - by Nakedible

  I'm interested in the actual real-word throughput attainable with an external 1000BaseT USB 2.0 network card under Linux. I have been able to attain 90 megabytes per second on a PCI-E interface, but the USB 2.0 bus has a theoretical limit of 480Mbit/s, and in practice less than 40 megabytes per second. Is the actual throughput attainable with such a card under linux 40, 30, 20, or even as low as 10 megabytes per second, eg. no better than a normal 100BaseT network card?

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• Maximise network transfer speed of various applications

  - by Alex

  When using nc, scp, wget to transfer files between 2 machines on a dedicated 2Mbps link, I get speeds between 0.5 and 1 Mbps. However, when I use iperf -c 10.0.1.4 -t 20 -P 12 (for example) I can maximise the speed of the link (getting stable 2Mbps). Is there a way to make single stream transfers (such as those done by scp) to utilise all/most of the link? Some kind of tcp settings, or iptables...?

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• Per process I/O accounting on AIX

  - by ipozgaj

  Is there a way of getting per process I/O statistics on AIX, i.e. to get current disk I/O rate of a process? Commands like iostat, nmon, topas etc. can't display such data. Filemon also doesn't help. Actually, what I would need is something much like iotop(1) command on Linux. Update: it seems there is no builtin command(s) to do this. I will most probably make my own by using the SPMI API.

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• Software solution from the 2000's, should I attempt to patch or remake the whole thing?

  - by ShadowScripter

  I was sent out to discuss a system that a certain company is currently using and what should be done with it. The company manufactures various carton displays. This system was developed to keep track of clients, orders and prices. Lots have happened since the system was created and the system is now, as the manager described it, "locked up" and "problematic", which I translate as "not dynamic" and "unstable". Some info about the system It was developed around the year 2000 Fairly small system, 2-5 users, 6 forms, ~8 tables with average quantities of data Built on early Visual Basic, forms created with the drag and drop design. Interface is basically just a window with a menu and some forms Uses MSSQL database (SQL2005 server) to store data and ODBC driver to query, data was migrated from excel before this system, and before excel it was handled, calculated and written by hand and paper Users work in Microsoft XP environment (and up) Their main problem is that they can't adjust and calculate prices, can't add new carton types etc, correctly anymore because they can't (or rather, they don't know how to) touch the data on the server. I suggested 3 possible solutions Attempt to patch the current system Create a fresh new interface (preferably similar environment, VB.net or VB based) Bring it back to an Excel solution, considering it is such a small system There might be more options, but these are the ones I could think of. My questions are What should I recommend and why? What is or could be the pros and cons of these alternatives? Are there other (possibly better) alternatives?

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• State Transition Constraints

  Data Validation in a database is a lot more complex than seeing if a string parameter really is an integer. A commercial world is full of complex rules for sequences of procedures, of fixed or variable lifespans, Warranties, commercial offers and bids. All this requires considerable subtlety to prevent bad data getting in, and if it does, locating and fixing the problem. Joe Celko shows how useful a State transition graph can be, and how essential it can become with the time aspect added.

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• BackupExec 12 + RALUS - VERY slow backups

  - by LVDave

  We use Backup Exec 12 and the Remote Agent for Linux/Unix Servers (RALUS) to backup a large RHEL5 system. For various reasons we need to do a daily working set job. These working-set jobs run abysmally slow. The link between the target machine and the BE server is gigabit, and any other type of job runs 1-3GB/min. These working-set jobs start out at perhaps 40MB/min and over the course of the backup job slowly drops down so low that the BE job rate display in the "current jobs" goes blank.. Since we usually are only doing changed-files for one day, the job is usually small and finishes overnight and we don't worry abotu the slowness, but we had some issues with the backup server, and missed about 6 days of fairly heavy work on the Linux box, so this working-set job will be a doozy.. We have support with Symantec, and I've pestered them a lot about this, they've had me run RALUS in debug mode, sent them that log and a VXgather from the BE host and they had no fix/workaround.. To give an idea, I have the mentioned working-set job running for the last 3 1/2 hours and it's backed up just under 10MEGAbytes.... I'm posting this here to see if anybody in the "real world" has seen this/and/or has any ideas what might be causing these abysmally slow jobs, since Symantec seems to be clueless...

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• mpstat on slackware 13.0 shows no utilization

  - by conartist6

  As the title says, the mpstat command, executed on Slack 13.0 continuously shows almost no processor utilization of any sort. In fact none of the output ever seems to change at all. The system is dual processor board with two hyperthreaded P4 Xeons. Any ideas? 08:50:06 PM CPU %user %nice %sys %iowait %irq %soft %steal %idle intr/s 08:50:06 PM all 0.38 0.00 0.03 0.03 0.00 0.00 0.00 99.56 1510.46 08:50:06 PM 0 0.50 0.00 0.05 0.10 0.00 0.01 0.00 99.33 11.90 08:50:06 PM 1 0.32 0.00 0.03 0.01 0.00 0.00 0.00 99.64 0.00 08:50:06 PM 2 0.38 0.00 0.03 0.01 0.00 0.00 0.00 99.58 0.00 08:50:06 PM 3 0.29 0.00 0.02 0.00 0.00 0.00 0.00 99.68 0.00 This is, literally, the only output I can get from the program. No values change ever.

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• A Tale of Identifiers

  Identifiers aren't locators, and they aren't pointers or links either. They are a logical concept in a relational database, and, unlike the more traditional methods of accessing data, don't derive from the way that data gets stored. Identifiers uniquely identify members of the set, and it should be possible to validate and verify them. Celko somehow involves watches and taxi cabs to illustrate the point.

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• cset shield --kthread on: should I use this?

  - by lori

  I'm reading up on cpu shielding using Alex Tsariounov's cset utility here: https://rt.wiki.kernel.org/index.php/Cpuset_Management_Utility/tutorial In the tutorial I'm finding the wording around migrating kernel threads from having access to all cpus to running only in a certain cpuset a bit ambiguous The tutorial says the following: Some kernel threads can be moved into the unshielded system cpuset as well. These are the threads that are not bound to specific CPUs. If a kernel thread is bound to a specific CPU, then it is generally not a good idea to move that thread to the system set because at worst it may hang the system and at best it will slow the system down significantly. These threads are usually the IRQ threads on a real time Linux kernel, for example, and you may want to not move these kernel threads into system. If you leave them in the root cpuset, then they will have access to all CPUs. The tutorial then goes on to say: However, if your application demands an even "quieter" shield, then you can move all movable kernel threads into the unshielded system set with the following command. [zuul:cpuset-trunk]# cset shield -k on cset: --> activating kthread shielding cset: kthread shield activated, moving 70 tasks into system cpuset... [==================================================]% cset: done I am confused by this final sentence. By using the word however, it seems to suggest that you typically should not move the movable kernel threads into the unshielded system set. Is this the case, or is it safe to move kernel threads which can be moved into a cpuset, thereby preventing them from running on some cpus?

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• High frequency, kernel bypass vs tuning kernels?

  - by Keith

  I often hear tales about High Frequency shops using network cards which do kernel bypass. However, I also often hear about them using operating systems where they "tune" the kernel. If they are bypassing the kernel, do they need to tune the kernel? Is it a case of they do both because whilst the network packets will bypass the kernel due to the card, there is still all the other stuff going on which tuning the kernel would help? So in other words, they use both approaches, one is just to speed up network activity and the other makes the OS generally more responsive/faster? I ask because a friend of mine who works within this industry once said they don't really bother with kernel tuning anymore-because they use kernel bypass network cards? This didn't make too much sense as I thought you would always want a faster kernel for all the CPU-offloaded calculations.

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• Why is piping dd through gzip so much faster than a direct copy?

  - by Foo Bar

  I wanted to backup a path from a computer in my network to another computer in the same network over a 100MBit/s line. For this I did dd if=/local/path of=/remote/path/in/local/network/backup.img which gave me a very low network transfer speed of something about 50 to 100 kB/s, which would have taken forever. So I stopped it and decided to try gzipping it on the fly to make it much smaller so that the amount to transfer is less. So I did dd if=/local/folder | gzip > /remote/path/in/local/network/backup.img.gz But now I get something like 1 MB/s network transfer speed, so a factor of 10 to 20 faster. After noticing this, I tested this on several paths and files and it was always the same. Why does piping dd through gzip also increase the transfer rates by a large factor instead of only reducing the bytelength of the stream by a large factor? I'd expected even a small decrease in transfer rates instead, due to the higher CPU consumption while compressing, but now I get a double plus. Not that I'm not happy, but just wondering. ;)

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• troubleshooting really slow login on a (linux) machine

  - by Peeter Joot

  Within the last couple of weeks, any attempt to login to a specific linux server has gotten really slow. Once I've logged in, things appear to run without significant delay, but some other login like activities (like starting a new screen session) are slow. The machine's been rebooted a couple of times recently and that hasn't helped. , and it doesn't appear to be $PATH search (where $PATH can sometimes include bad NFS mounts), which I've seen historically in our environment. I've also tried completely removing my .profile/.bash*/... type of init files to rule out anything bad there. I also see slow login for at least one other userid on the system. One thing I've noticed is the following message when trying to exit from a screen terminal: Utmp slot not found -> not removed and am wondering if this is related (having a vague recollection that Utmp has something to do with login). Any idea what that message means, or how to fix it, and if it would be related? Failing that, what sort of problem determination tools are available to investigate what is slowing down this login process?

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• Microsoft Azure Outage

  The beginning of Azure's troubles was documented last Wednesday at approximately 1:45 a.m. GMT when its service management component malfunctioned. The initial message on the outage, posted by Microsoft on its Azure service dashboard, read: We are experiencing an issue with Windows Azure service management. Customers will not be able to carry out service management operations. Microsoft continued with its updates at 5 a.m. GMT, when it assured users that fewer than 3.8 percent of hosted services had been affected by the outage. The company also said it was doing its best to stop the issue ...

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• SQL SERVER Disabled Index and UpdateStatistics

  When we try to update the statistics, it throws an error as if the clustered index is disabled. Now let us enable the clustered index only and attempt to update the statistics of the table right after that. Have you ever come across the situation where a conversation never gets over and it continues even [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• How do you disable the magnifier in Windows Vista?

  - by PhantomDrummer

  Every so often while I'm working, if I accidentally jolt the mouse, the magnifier starts. I'm fairly sure the cause is that some comination of mouse keys is supposed to start the magnifier, and I occasionally hit the right keys accidentally. However, I've never been able to reproduce the behaviour deliberately so I don't know which combination. This is very annoying since switching the magnifier off is non-trivial (control panel, or run dialog, which are hard to use when the magnifier keeps - ummm - windowing and magnifying the bit of screen you're about to click on :-) ). So I'm wondering if there's any way to disable the magnifier completely, so that it doesn't start when you do whatever it is you'd normally do to the mouse to start it? Anyone know?

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• Load testing nginx inside AWS

  - by andy

  I'm trying to load test nginx running on AWS. I need to try to optimise it to handle 1Gbps of inbound traffic. Currently I've got it to peak at 85Mbit/s by running nginx on an m1.large with 4 other machines hitting it by using ab with -i (for head requests) -k (keepalives) -r (ignore failed requests) -n 500000 -c 20000. I'm struggling to generate more than 85 Mbit/s traffic from 4 machines, yet when I do scp a large file I get nearly 0.25Gbit/s of traffic going over the network. Are there any tools or approaches that I could use to load test nginx that might generate more load? I'm only interested in inbound traffic, so perhaps a DoS tool could help if it chucks away responses? I'm hitting a very small (40 byte) static asset, and have peaked at handling 50K concurrent connections and getting 25k reqs/s when just using a single load generator machine.

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• Linux: find out what process is using all the RAM?

  - by Timur

  Before actually asking, just to be clear: yes, I know about disk cache, and no, it is not my case :) Sorry, for this preamble :) I'm using CentOS 5. Every application in the system is swapping heavily, and the system is very slow. When I do free -m, here is what I got: total used free shared buffers cached Mem: 3952 3929 22 0 1 18 -/+ buffers/cache: 3909 42 Swap: 16383 46 16337 So, I actually have only 42 Mb to use! As far as I understand, -/+ buffers/cache actually doesn't count the disk cache, so I indeed only have 42 Mb, right? I thought, I might be wrong, so I tried to switch off the disk caching and it had no effect - the picture remained the same. So, I decided to find out who is using all my RAM, and I used top for that. But, apparently, it reports that no process is using my RAM. The only process in my top is MySQL, but it is using 0.1% of RAM and 400Mb of swap. Same picture when I try to run other services or applications - all go in swap, top shows that MEM is not used (0.1% maximum for any process). top - 15:09:00 up 2:09, 2 users, load average: 0.02, 0.16, 0.11 Tasks: 112 total, 1 running, 111 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 4046868k total, 4001368k used, 45500k free, 748k buffers Swap: 16777208k total, 68840k used, 16708368k free, 16632k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ SWAP COMMAND 3214 ntp 15 0 23412 5044 3916 S 0.0 0.1 0:00.00 17m ntpd 2319 root 5 -10 12648 4460 3184 S 0.0 0.1 0:00.00 8188 iscsid 2168 root RT 0 22120 3692 2848 S 0.0 0.1 0:00.00 17m multipathd 5113 mysql 18 0 474m 2356 856 S 0.0 0.1 0:00.11 472m mysqld 4106 root 34 19 251m 1944 1360 S 0.0 0.0 0:00.11 249m yum-updatesd 4109 root 15 0 90152 1904 1772 S 0.0 0.0 0:00.18 86m sshd 5175 root 15 0 90156 1896 1772 S 0.0 0.0 0:00.02 86m sshd Restart doesn't help, and, by they way is very slow, which I wouldn't normally expect on this machine (4 cores, 4Gb RAM, RAID1). So, with that - I'm pretty sure that this is not a disk cache, who is using the RAM, because normally it should have been reduced and let other processes to use RAM, rather then go to swap. So, finally, the question is - if someone has any ideas how to find out what process is actually using the memory so heavily?

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• High Steal Time utilization on Apache Linux Server

  - by JMC

  I have a CentOS "development / testing" server that runs extremely slowly. It's running Apache and Mysql using PHP. Top reports that 98% of the CPU utilization is frequently spent on "st" - Steal Time. What could cause a server to spend so much CPU on steal time, and how can I diagnose the problem? I didn't notice the problem until after I granted a third party developer root access (for all I know it has a root kit running, though unlikely).

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• Apache's htcacheclean doesn't scale: How to tame a huge Apache disk_cache?

  - by flight

  We have an Apache setup with a huge disk_cache (500.000 entries, 50 GB disk space used). The cache grows by 16 GB every day. My problem is that the cache seems to be growing nearly as fast as it's possible to remove files and directories from the cache filesystem! The cache partition is an ext3 filesystem (100GB, "-t news") on an iSCSI storage. The Apache server (which acts as a caching proxy) is a VM. The disk_cache is configured with CacheDirLevels=2 and CacheDirLength=1, and includes variants. A typical file path is "/htcache/B/x/i_iGfmmHhxJRheg8NHcQ.header.vary/A/W/oGX3MAV3q0bWl30YmA_A.header". When I try to call htcacheclean to tame the cache (non-daemon mode, "htcacheclean-t -p/htcache -l15G"), IOwait is going through the roof for several hours. Without any visible action. Only after hours, htcacheclean starts to delete files from the cache partition, which takes a couple more hours. (A similar problem was brought up in the Apache mailing list in 2009, without a solution: http://www.mail-archive.com/[email protected]/msg42683.html) The high IOwait leads to problems with the stability of the web server (the bridge to the Tomcat backend server sometimes stalls). I came up with my own prune script, which removes files and directories from random subdirectories of the cache. Only to find that the deletion rate of the script is just slightly higher than the cache growth rate. The script takes ~10 seconds to read the a subdirectory (e.g. /htcache/B/x) and frees some 5 MB of disk space. In this 10 seconds, the cache has grown by another 2 MB. As with htcacheclean, IOwait goes up to 25% when running the prune script continuously. Any idea? Is this a problem specific to the (rather slow) iSCSI storage? Should I choose a different file system for a huge disk_cache? ext2? ext4? Are there any kernel parameter optimizations for this kind of scenario? (I already tried the deadline scheduler and a smaller read_ahead_kb, without effect).

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• What does the 'Burst Rate' stat mean in HDTune?

  - by UpTheCreek

  I recently upgraded my laptop's v slow hard drive to a seagate momentus 7200. Everything is working fine, but I'm a bit confused by these benchmark results: The burst rate is significantly less than the Maximim transfer rate, and not much higher than the normal minimum (if you ignore the spikes). What's going on here? On the HDtune website it defines Burst Rate as: ...the highest speed (in megabytes per second) at which data can be transferred from the drive interface (IDE or SCSI for example) to the operating system. Which begs some questions... e.g. if this is the highest, then how did the bechmarking tool record the 103MB/sec maximum? And if this really is the true maximum, then where is the bottleneck? The laptops SATA interface is on an Intel 82801GBM southbridge controller. When I check in hardware manager, I see that it's driver is iaStor.sys from 2005. Maybe that's the issue? I'll look for a newever version, but any insights would be appreciated. Thanks

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• c# display DB table structure

  - by user3529643

  I have a question. My code is the following : public partial class Form1 : Form { public OleDbConnection datCon; public string MyDataFile; public ArrayList tblArray; public ArrayList fldArray; public Form1() { InitializeComponent(); lvData.Clear(); lvData.View = View.Details; lvData.LabelEdit = false; lvData.FullRowSelect = true; lvData.GridLines = true; } private void DataConnection() { MyDataFile = Application.StartupPath + @"\studenti.mdb"; string MyCon = @"provider=microsoft.jet.oledb.4.0;data source=" + MyDataFile; try { datCon = new OleDbConnection(MyCon); } catch (Exception ex) { MessageBox.Show(ex.Message); } FillTreeView(); } private void GetTables(OleDbConnection cnn) { try { cnn.Open(); DataTable schTable = cnn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new Object[] { null, null, null, "TABLE" }); tblArray = new ArrayList(); foreach (DataRow datrow in schTable.Rows) { tblArray.Add(datrow["TABLE_NAME"].ToString()); } cnn.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void GetFields(OleDbConnection cnn, string tabNode) { string tabName; try { tabName = tabNode; cnn.Open(); DataTable schTable = cnn.GetOleDbSchemaTable(OleDbSchemaGuid.Columns, new Object[] { null, null, tabName }); fldArray = new ArrayList(); foreach (DataRow datRow in schTable.Rows) { fldArray.Add(datRow["COLUMN_NAME"].ToString()); } cnn.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void FillTreeView() { tvData.Nodes.Clear(); tvData.Nodes.Add("Database"); tvData.Nodes[0].Tag = "RootDB"; GetTables(datCon); // add table node for (int i = 0; i < tblArray.Count; i++) { tvData.Nodes[0].Nodes.Add(tblArray[i].ToString()); tvData.Nodes[0].Nodes[i].Tag = "Tables"; } // add field node for (int i = 0; i < tblArray.Count; i++) { GetFields(datCon, tblArray[i].ToString()); for (int j = 0; j < fldArray.Count; j++) { tvData.Nodes[0].Nodes[i].Nodes.Add(fldArray[j].ToString()); tvData.Nodes[0].Nodes[i].Nodes[j].Tag = "Fields"; } } this.tvData.ContextMenuStrip = contextMenuStrip1; contextMenuStrip1.ItemClicked +=contextMenuStrip1_ItemClicked; } public void FillListView(OleDbConnection cnn, string tabName) { OleDbCommand cmdRead; OleDbDataReader datReader; string strField; lblTableName.Text = tabName; strField = "SELECT * FROM [" + tabName + "]"; // Initi cmdRead obiect cmdRead = new OleDbCommand(strField, cnn); cnn.Open(); datReader = cmdRead.ExecuteReader(); // fill ListView while (datReader.Read()) { ListViewItem objListItem = new ListViewItem(datReader.GetValue(0).ToString()); for (int c = 1; c < datReader.FieldCount; c++) { objListItem.SubItems.Add(datReader.GetValue(c).ToString()); } lvData.Items.Add(objListItem); } datReader.Close(); cnn.Close(); } private void ViewToolStripMenuItem_Click(object sender, EventArgs e) { DataConnection(); } public void tvData_AfterExpand(object sender, System.Windows.Forms.TreeViewEventArgs e) { string tabName; int fldCount; if (e.Node.Tag.ToString() == "Tables") { fldCount = e.Node.GetNodeCount(false); //column headers. int n = lvData.Width; double wid = n / fldCount; // width columnn for (int c = 0; c < fldCount; c++) { lvData.Columns.Add(e.Node.Nodes[c].Text, (int)wid, HorizontalAlignment.Left); } // gett table name tabName = e.Node.Text; FillListView(datCon, tabName); } } public void button1_Click(object sender, EventArgs e) { //TO DO?? } } I have a treeview populated with tables (nodes) from my database, and a listview which is populated with the data from my tables when I click on a table. As you can see I have a button1 on my form. When I click it I want it to display to me the structure of the table I selected in my treeview (a treeview node). Not too many details, just the name of the columns in my table, type of columns, primary keys. I've tried to follow many tutorials but I can t seem to manage it.

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• What to do before trying to benchmark

  - by user23950

  What are the things that I should do before trying to benchmark my computer: I've got this tools for benchmarking: 3dmark cinebench geekbench juarez dx10 open source mark Do I need to have a full spyware and virus scan before proceeding?What else should I do, in order to get accurate readings.

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• How can I determine Breaking point of my Web application using JMeter?

  - by Gopu Alakrishna

  How can I determine Breaking point of my Web application using JMeter? I have executed the JMeter Testplan with different concurrent users load. EX. 300 users(0% error), 400 users(7% error in a sample, 5% error in another sample), 500 users(more than 10% error in 4 out of 6 samples). At What value of % Error, I can say system reached the Breaking point.I used concurrent users 300, 400, 500 in a PHP website. Should I consider any other parameter to determine breaking point. How many maximum concurrent users my application can support?

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