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Re: [zfs-discuss] Performance issues with iSCSI under Linux

Subject: Re: [zfs-discuss] Performance issues with iSCSI under Linux
From: Phil Harman
Date: Fri, 15 Oct 2010 07:47:08 +0100

It would help to have some config detail (e.g. what options are you using? 
zpool status output; property lists for specific filesystems and zvols; etc)

Some basic Solaris stats can be very helpful too (e.g. peak flow samples of 
vmstat 1, mpstst 1, iostat -xnz 1, etc)

It would also be great to know how you are running you tests.

I'd also like to know what version of NFS and mount options. A network trace 
down to NFS RPC or iSCSI operation level with timings would be great too.

I'm wondering whether your HBA has a write through or write back cache enabled? 
The latter might make things very fast, but could put data at risk if not 
sufficiently non-volatile.


On 14 Oct 2010, at 22:02, Ian D <[email protected]> wrote:

>> Our next test is to try with a different kind of HBA,
>> we have a Dell H800 lying around.
> ok... we're making progress.  After swapping the LSI HBA for a Dell H800 the 
> issue disappeared.  Now, I'd rather not use those controllers because they 
> don't have a JBOD mode. We have no choice but to make individual RAID0 
> volumes for each disks which means we need to reboot the server every time we 
> replace a failed drive.  That's not good...
> What can we do with the LSI HBA?  Would you call LSI's support?  Is there 
> anything we should try besides the obvious (using the latests 
> firmware/driver)?
> To resume the issue, when we copy files from/to the JBODs connected to that 
> HBA using NFS/iSCSI, we get slow transfer rate <20M/s and a 1-2 second pause 
> between each file.   When we do the same experiment locally using the 
> external drives as a local volume (no NFS/iSCSI involved) then it goes upward 
> of 350M/sec with no delay between files. 
> Ian
> Message was edited by: reward72
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