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john57
Joined: 09 Feb 2012
Posts: 3
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| Posted: Thu Feb 09, 2012 5:43 am Post subject: Disk I/O test |
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UK datacenter
Code: free -m
ok...
Code: htop
ok...
Code: w
~idle...
Code: df -h
ok...
Code: dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync
~5 MB/s
15 minutes later...
~7 MB/s
(Linode 512 @ UK)
temporary? |
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hybinet
Joined: 02 May 2008
Posts: 1058
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| Posted: Thu Feb 09, 2012 8:11 am Post subject: |
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Since when is "dd" a valid test of disk I/O performance? It only measures sequential I/O performance with one big sync at the end, which is very different from the random I/O pattern that most websites and databases require.
The Webhostingtalk crowd loves to compare these meaningless numbers, which makes some VPS hosts modify their settings to look good on specific versions of the "dd" test. I've seen numbers upwards of 200MB/s on OpenVZ hosts. Many of those hosts still suck at actual database performance.
I don't know what the usual "dd" numbers for a Linode 512 are (and I'm not going to hammer the disk with an empty 1GB file just for the sake of finding out), but what really matters is how your application is performing. Do your web pages load quickly? Do your database queries finish quickly? |
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pclissold
Joined: 24 Oct 2003
Posts: 877
Location: Netherlands
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| Posted: Thu Feb 09, 2012 8:40 am Post subject: |
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hybinet wrote: … and I'm not going to hammer the disk with an empty 1GB file just for the sake of finding out…
I will, then :D (on a 768 -- it's the nearest I've got to a 512) -- 107 MB/s, so the OPs numbers do seem low. |
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hybinet
Joined: 02 May 2008
Posts: 1058
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| Posted: Thu Feb 09, 2012 9:11 am Post subject: |
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pclissold wrote: 107 MB/s, so the OPs numbers do seem low.
Quite possible, if the OP is on a newly deployed Linode that shares the host with 39 other newly deployed Linodes, all frantically apt-getting their LAMP stacks. Even when that happens, disk performance is generally OK.
But even your number is going to look low to someone who is used to seeing 200MB/s+ on OpenVZ hosts specifically designed for dd tests. And those hosts use consumer-grade 7200rpm disks. |
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john57
Joined: 09 Feb 2012
Posts: 3
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| Posted: Fri Feb 17, 2012 4:58 am Post subject: |
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Linode techs: please check this, ~5MB/s (avg, different days) is unacceptable.
I know you couldn't care less (just a cheap 512...), but we are cancelling our account at linode this month (if you don't fix this). |
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phyber
Joined: 15 Apr 2011
Posts: 8
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| Posted: Fri Feb 17, 2012 5:06 am Post subject: |
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john57 wrote: Linode techs: please check this
If you really want them to check this out, your best bet is to submit a support ticket instead of hoping that they spot this thread on the forums. |
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GLaDOSDan
Joined: 25 Nov 2010
Posts: 23
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| Posted: Fri Feb 17, 2012 5:07 am Post subject: |
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john57 wrote: Linode techs: please check this, ~5MB/s (avg, different days) is unacceptable.
I know you couldn't care less (just a cheap 512...), but we are cancelling our account at linode this month (if you don't fix this).
They do care about Linode 512s just as much as the $800/mo plans. Your best bet is to open a support ticket, I'm sure they'll look into it for you.
My 512 gets a very respectable 95MB/s with the dd line you pasted. |
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jebblue
Joined: 23 May 2010
Posts: 112
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| Posted: Fri Feb 17, 2012 1:26 pm Post subject: |
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john57 wrote: Linode techs: please check this, ~5MB/s (avg, different days) is unacceptable.
I know you couldn't care less (just a cheap 512...), but we are cancelling our account at linode this month (if you don't fix this).
Did you contact support and file a ticket? Linode has the best support, fastest response time, nicest and smartest people of any host I was ever with and that's several. |
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