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Re: [Xen-API] [XCP 1.6 beta] poor performance while importing vm template


On 03.10.2012 09:32, SpamMePlease PleasePlease wrote:
Have you tried basic disk read or write throughput tests on these disks like
running a:
dd if=/dev/zero of=test bs=1M count=2000 oflag=direct

While doing so, the io wait also skyrockets (up to ~60%), along with
load average (up to ~2), with the average speed of 12,8 MB/s. However,
the hdparm reports as below:
That is very slow write performance for 1megs blocks. Doing the same test on dell box here (with 500mb because i have not enough free space to do the 2gig test)

[root@xen-blade11 tmp]# dd if=/dev/zero of=test bs=1M count=500 oflag=direct
500+0 records in
500+0 records out
524288000 bytes (524 MB) copied, 2.08047 seconds, 252 MB/s

That might be where you should start investigating. Does your controller has write-back enabled (instead of write-through) ?

  Timing cached reads:   23680 MB in  1.99 seconds = 11887.43 MB/sec
  Timing buffered disk reads: 492 MB in  3.01 seconds = 163.45 MB/sec

That is caching reads test, this is kinda irrelevant for large data transfers.
I might be wrong but for me you have an issue with write throughput.


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