On 07/07/2009, at 8:20 PM, James Andrewartha wrote:
Have you tried putting the slog on this controller, either as an SSD
or
regular disk? It's supported by the mega_sas driver, x86 and amd64
only.
What exactly are you suggesting here? Configure one disk on this
array as a dedicated ZIL? Would that improve performance any over
using all disks with an internal ZIL?
I have now done some tests with the PERC6/E in both RAID10 (all
devices RAID0 LUNs, ZFS mirror/striped config) and also as a hardware
RAID5 both with an internal ZIL.
RAID10 (10 disks, 5 mirror vdevs)
create 2m14.448s
unlink 0m54.503s
RAID5 (9 disks, 1 hot spare)
create 1m58.819s
unlink 0m48.509s
Unfortunately, linux on the same RAID5 array using XFS seems
significantly faster, still.
Linux RAID5 (9 disks, 1 hot spare), XFS
create 1m30.911s
unlink 0m38.953s
Is there a way to disable the write barrier in ZFS in the way you can
with Linux filesystems (-o barrier=0)? Would this make any difference?
After much consideration, the lack of barrier capability makes no
difference to filesystem stability in the scenario where you have a
battery backed write cache.
Due to using identical hardware and configurations, I think this is a
fair apples to apples test now. I'm now wondering if XFS is just the
faster filesystem... (not the most practical management solution, just
speed).
cheers,
James
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