Possibly the storage is flushing the write caches when it
should not. Until we get a fix, cache flushing could be
disabled in the storage (ask the vendor for the magic
incantation). If that's not forthcoming and if all pools are
attached to NVRAM protected devices; then these /etc/system
evil tunable might help :
In older solaris releases we have
set zfs:zil_noflush = 1
On newer releases
set zfs:zfs_nocacheflush = 1
If you implement this, Do place a comment that this is a
temporary workaround waiting for bug 6462690 to be fixed.
About Compression, I don't have the numbers but a reasonable
guess would be that it can consumes roughly 1-Ghz of CPU to
compress 100MB/sec. This will of course depend on the type
of data being compressed.
-r
Roshan Perera writes:
> Hi all,
>
> I am after some help/feedback to the subject issue explained below.
>
> We are in the process of migrating a big DB2 database from a
>
> 6900 24 x 200MHz CPU's with Veritas FS 8TB of storage Solaris 8 to
> 25K 12 CPU dual core x 1800Mhz with ZFS 8TB storage SAN storage
> (compressed & RaidZ) Solaris 10.
>
> Unfortunately, we are having massive perfomance problems with the new
> solution. It all points towards IO and ZFS.
>
> Couple of questions relating to ZFS.
> 1. What is the impace on using ZFS compression ? Percentage of system
> resources required, how much of a overhead is this as suppose to
> non-compression. In our case DB2 do similar amount of read's and
> writes.
> 2. Unfortunately we are using twice RAID (San level Raid and RaidZ) to
> overcome the panic problem my previous blog (for which I had good
> response).
> 3. Any way of monitoring ZFS performance other than iostat ?
> 4. Any help on ZFS tuning in this kind of environment like caching etc ?
>
> Would appreciate for any feedback/help wher to go next.
> If this cannot be resolved we may have to go back to VXFS which would be a
> shame.
>
>
> Thanks in advance.
>
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss@opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
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