Miguel Gonzalez Castaños escribió:
> Hi,
>   I've been recommended by Mike Christie to perform raw benchmarks with 
> disktest:
>   for reads:
>   disktest -PT -T30  -K32 -B128k -ID /dev/sdXYZ -h1
>   for writes:
>   disktest -PT -T30  -K32 -B128k -ID /dev/sdXYZ -h1 -D 0:100
>   I'm testing virtual machines using iSCSI. Virtual Server has a 
> bottleneck with the network emulation. It works fine for the rest of the 
> services but not for iSCSI.
>   I've tried with VMware, and honestly, the best performance I get is 
> using the iSCSI Windows initiator and create the virtual hard drive on 
> the Windows partition that I create through iSCSI.
>   However, I'm still trying to compare direct iSCSI from linux versus 
> hard drives created on iSCSI windows partitions but using the 
> filesystem. I've tried using:
>   dd if=/dev/zero of=/mnt/virtualdata1/zero bs=4096 count=1572864
>   dd if=/mnt/virtualdata1/zero of=/dev/null bs=4096
>   and then I get very low performances (around 10-14 MB/s) or even less.
>   While testing raw performance the difference is huge:
>    disk on iSCSI Windows Reads: 1759.08MB/s Writes: 93.70MB/s
>    disk using open-iscsi  Reads: 35.84MB/s Writes: 57.39MB/s
>     I've tried changing MTU, and only changing the scheduler to noop I 
> get better reads performance.
>     But when It comes to filesystem, apparently performances are pretty 
> more the same. Maybe dd is not very reliable? (I've tested it and kill 
> the process in about one minute and the numbers vary a lot)
I've found that changing the mount options of ext3 to noatime,nodiratime 
the performance improves a lot, anyone knows if it is a good idea to use 
this settings?



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