Have you tried creating tank/bkp without the -s option. I believe I read
somewhere that the -s option can lead to poor performance on larger
volumes (which doesn't make sense to me). Also are you using a zil/log
device?
Josh Simon
On 06/29/2010 09:33 AM, Effrem Norwood wrote:
Hi All,
I created a zvol with the following options on an X4500 with 16GB of ram:
zfs create -s -b 64K -V 250T tank/bkp
I then enabled dedup and compression and exported it to Windows Server
2008 as iSCSI via COMSTAR. There it was formatted with a 64K cluster
size which is the NTFS default for volumes of this size. IO performance
in Windows is so slow that my backup jobs are timing out. Previously
when I created a much smaller volume using a “-b” of 4K and NTFS cluster
size of 4K performance was excellent. What I would like to know is what
to look at to figure out where the performance is going, e.g. it’s the
blocksize or it’s COMSTAR etc. CPU consumption according to top is very
low so compression seems unlikely. The L2ARC is 11G and there is 4G + of
free memory and no swapping so dedup seems unlikely as well. I have
looked at the latencytop utility for clues but am not familiar enough
with the code to conclude anything useful.
Thanks!
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