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08-23-2011, 07:31 PM #1WHT Addict
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How to test I/O performance without using the famous dd command
few days ago I have signed up a managed vps. After optimizing and initial setup, I ran the dd command to test the I/O performance:
dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync
and it wasn't impressed at all, I never get anything higher than 3xmb/s, most of the time I got 2xmb/s, and sometimes 1xmb/s
I have contacted my vps provider and told them the situation, either they tried to convince me by running:
dd if=/dev/zero of=test bs=1M count=1024
(without conv=fdatasync)
(for those who want to know the difference with or without conv=fdatasync please see this article http://www.lowendbox.com/blog/hostra...#comment-14744)
or telling me there is no problem, server is not overloaded etc and asked me if my vps is sluggish or not. There's not much help from them
At this moment I still haven't migrated any of my website to this new vps, as I want to make sure everything is fine to do so. If not, I'm not gonna keep it for another month. So besides using the dd command, is there anything I can run to test the disk performance or check if the node is overloaded. I'm running openvz w/centos 6.
Thanks in advance
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08-23-2011, 07:38 PM #2Aspiring Evangelist
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Please be careful with your units. A bit is not equal to a byte and the units are abbreviated with very specific capitalization so that we can all interpret them properly. 10MB/s is not the same as 10mb/s. Are you saying that you got 3mb/s as a result from dd? As in three mega BITS per second? Please copy/past the output directly from dd without modifying it and we'll be able to interpret it more accurately.
What are the results using this dd syntax? Even a regular old SATA hard drive should be able to easily achieve 10MB/s. It does sound like there's something not quite right with this situation.Cheap VPS Hosting with minimum 99.9% SLA.
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08-23-2011, 07:42 PM #3WHT Addict
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sorry, when i said 2xmb/s or 1xmb/s I meant the numbers betwen 20-29 or 10-19
here is what i got:
dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 47.6071 s, 22.6 MB/s
sorry if it confused you
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08-23-2011, 07:45 PM #4Aspiring Evangelist
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Ahh now I understand. I guess I should have seen the x in there. Sorry about that!
That's not GREAT, but it's not terrible. I think for most the low-end VPS providers, that is pretty much the going average. If that's not good enough and you ARE on a low-end provider, it's probably time to move up. If you are on a HIGH-end provider, or even a middle of the road provider, you are very correct in escalating this to their support. I hope you get a resolution soon!
Best,
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08-24-2011, 01:42 AM #5Junior Guru
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When you next send in a support ticket/reply about this, give them a link to this thread so they can learn a few things.
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08-24-2011, 04:49 AM #6Web Hosting Master
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What number impresses you? And how often would you have to do a sequential write to a large file?
If it does not affect the operation of your server, why bother? You might get better performance when you move on to the next provider, but doesn't mean the performance will last forever. Things will turn slower and slower gradually as soon as more VMs are running.
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08-24-2011, 04:57 AM #7Web Hosting Master
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root@vps [~]# dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 7.61077 seconds, 141 MB/s
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08-24-2011, 06:07 AM #8Web Hosting Master
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dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 3.59642 seconds, 299 MB/s
As already said unless you plan to do allot of sequential writes to a large file the dd test is meaningless however you did ask for a way to test IO performance so before this thread turns in to a "my balls are bigger than yours dd thread"
You should be doing a number of tests to benchmark your whole VPS not just the disk.
Unixbench
Geekbench
ioping (very important for disk) http://code.google.com/p/ioping/
Is your VPS on 1000 or 100mbit if 1000 mbit can you download files faster that the dd test can write, if so consider the logic█ -> INCEPTION HOSTING LIMITED Since 2010!
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08-24-2011, 06:35 AM #9Junior Guru Wannabe
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I'm getting 87.6MB/s on Linode and 77.1MB/s on Burstnet (low end) server. Just throwing that in for comparison.
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08-24-2011, 06:41 AM #10Web Hosting Master
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This is not an accurate test of IO speed.
Please try hdparm -t /dev/sda.
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08-24-2011, 07:04 AM #11Aspiring Evangelist
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08-24-2011, 08:22 AM #12Web Hosting Evangelist
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Also try looking at ioping to test disk latency.
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08-24-2011, 10:23 AM #13Newbie
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08-24-2011, 05:24 PM #14Aspiring Evangelist
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There's a good amount of information here: http://code.google.com/p/ioping/
If you're using BSD or another UNIX operating system, change the devices accordingly.
Code:Usage: ioping [-LCDRq] [-c count] [-w deadline] [-p period] [-i interval] [-s size] [-S wsize] [-o offset] device|file|directory ioping -h | -v -c <count> stop after <count> requests -w <deadline> stop after <deadline> -p <period> print raw statistics for every <period> requests -i <interval> interval between requests (1s) -s <size> request size (4k) -S <wsize> working set size (1m) -o <offset> in file offset -L use sequential operations (includes -s 256k) -C use cached I/O -D use direct I/O -R seek rate test (same as -q -i 0 -w 3 -S 64m) -q suppress human-readable output -h display this message and exit -v display version and exit
Code:$ ioping . 4096 bytes from . (ext4 /dev/sda3): request=1 time=0.2 ms 4096 bytes from . (ext4 /dev/sda3): request=2 time=0.2 ms 4096 bytes from . (ext4 /dev/sda3): request=3 time=0.3 ms 4096 bytes from . (ext4 /dev/sda3): request=4 time=12.7 ms 4096 bytes from . (ext4 /dev/sda3): request=5 time=0.3 ms ^C --- . (ext4 /dev/sda3) ioping statistics --- 5 requests completed in 4794.0 ms, 364 iops, 1.4 mb/s min/avg/max/mdev = 0.2/2.8/12.7/5.0 ms Measure disk seek rate (iops, avg)
Code:--- /dev/sda (device 465.8 Gb) ioping statistics --- 186 requests completed in 3004.6 ms, 62 iops, 0.2 mb/s min/avg/max/mdev = 6.4/16.0/26.8/4.7 ms Measure disk sequential speed (mb/s)
Code:--- /dev/sda (device 465.8 Gb) ioping statistics --- 837 requests completed in 3004.1 ms, 292 iops, 72.9 mb/s min/avg/max/mdev = 2.0/3.4/28.9/2.0 ms
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08-24-2011, 05:30 PM #15Web Hosting Master
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08-24-2011, 06:41 PM #16WHT Addict
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so here is what i got:
ioping -c 10 /
4096 bytes from / (simfs /dev/simfs): request=1 time=0.1 ms
4096 bytes from / (simfs /dev/simfs): request=2 time=0.1 ms
4096 bytes from / (simfs /dev/simfs): request=3 time=0.1 ms
4096 bytes from / (simfs /dev/simfs): request=4 time=0.1 ms
4096 bytes from / (simfs /dev/simfs): request=5 time=3708.7 ms
4096 bytes from / (simfs /dev/simfs): request=6 time=0.1 ms
4096 bytes from / (simfs /dev/simfs): request=7 time=1033.5 ms
4096 bytes from / (simfs /dev/simfs): request=8 time=447.4 ms
4096 bytes from / (simfs /dev/simfs): request=9 time=110.7 ms
4096 bytes from / (simfs /dev/simfs): request=10 time=11.1 ms
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08-24-2011, 06:52 PM #17Web Hosting Master
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0.1 = fine
0.1 = fine
0.1 = fine
0.1 = fine
3708.7 = Jesus H!!
0.1 = fine
etc etc.
The odd spike is not unusual, someone else may have been giving it dd's at the time, for a real test you should be looking at 1000 minimum
If you cba to wait for it just echo the results to a file with '> ioping.txt &' at the end of the command and check the results when its finished.
Again the odd spike is normal but if you start getting, I dunno 10 - 20 nasty results in a row just sent the output to your host and ask what's going on, I suspect they wont have an answer though based on the previous info you gave.
Would be interesting to see your unix or geek bench scores too just as general reference.█ -> INCEPTION HOSTING LIMITED Since 2010!
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08-24-2011, 07:43 PM #18WHT Addict
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my ioping result:
PHP Code:tail -f ioping.result
4096 bytes from / (simfs /dev/simfs): request=995 time=0.1 ms
4096 bytes from / (simfs /dev/simfs): request=996 time=0.2 ms
4096 bytes from / (simfs /dev/simfs): request=997 time=1293.9 ms
4096 bytes from / (simfs /dev/simfs): request=998 time=31.0 ms
4096 bytes from / (simfs /dev/simfs): request=999 time=0.2 ms
4096 bytes from / (simfs /dev/simfs): request=1000 time=0.2 ms
--- / (simfs /dev/simfs) ioping statistics ---
1000 requests completed in 1073183.8 ms, 14 iops, 0.1 mb/s
min/avg/max/mdev = 0.0/73.1/7576.7/491.7 ms
http://browse.geekbench.ca/geekbench2/view?id=469968
I paid $25+ for this, not sure if I should keep it or not, please advise
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08-24-2011, 08:01 PM #19Web Hosting Master
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The GB score is actually pretty decent, and if you mean $25 p/year then its very good (compare this score with some of the ones on http://96mb.com for reference)
However.... your abv result in the ioping result is not good, if you can work with your provider to work this out then its a keeper I would say.
I suppose the bottom line though.... apart from the perceived low performance from dd (which is not all that relevant) is it actually affecting you and is anything suffering, if not then its not the end of the world.█ -> INCEPTION HOSTING LIMITED Since 2010!
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08-24-2011, 08:06 PM #20WHT Addict
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of course not, i paid $25+/mo
I have already contacted them regarding the disk, I even sent them the dd result that I got (around 20ish mb/s) it just they keep saying there is no problem...
Anyways will try to send the latest ioping result, if they are still in denial then I'll ask for a refund and post my honest review on wht.
Anyways thanks backtogeek
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