Vincent Fox writes:
> I don't understand. How do you
>
> "setup one LUN that has all of the NVRAM on the array dedicated to it"
>
> I'm pretty familiar with 3510 and 3310. Forgive me for being a bit
> thick here, but can you be more specific for the n00b?
>
> Do you mean from firmware side or OS side? Or since the LUNs used
> for the ZIL are separated out from the other disks in the pool they DO
> get to make use of the NVRAM, is that it?
>
> I have a pair of 3310 with 12 36-gig disks for testing. I have a
> V240 with PCI dual-SCSI controller so I can drive one array from each
> port is what I am tinkering with right now. Looking for maximum
> reliability/redundancy of course so I would ZFS mirror the arrays.
>
> Can you suggest a setup here? A single-disk from each array
> exported as a LUN, then ZFS mirrored together for the ZIL log?
> An example would be helpful. Could I then just lump all the
> remaining disks into a 10-disk RAID-5 LUN, mirror them together
> and achieve a significant performance improvement? Still have
> to have a global spare of course in the HW RAID. What about
> sparing for the ZIL?
>
With
PSARC 2007/171 ZFS Separate Intent Log
now in Nevada, you can setup the ZIL on it's own set of
(possibly very fast) luns. The luns can be mirrored if you
have more than one NVRAM cards.
http://blogs.sun.com/perrin/entry/slog_blog_or_blogging_on
This will work great to accelerate JBOD using just a small
amount of NVRAM for the ZIL. When a storage is fronted 100%
by NVRAM the benefits of the slog won't be as large.
Last week we had this putback :
PSARC 2007/053 Per-Disk-Device support of non-volatile cache
6462690 sd driver should set SYNC_NV bit when issuing SYNCHRONIZE CACHE
to SBC-2 devices
which will prevent some recognised Arrays from doing
unnecessary cache flushes and allow tuning others using
sd.conf. Otherwise arrays will be queried for support of the
SYNC_NV capability. IMO, the best is to bug storage vendors
into supporting SYNC_NV.
For earlier releases, to get the full benefit of the NVRAM on
zil operations you are stuck into a raw tuning proposition :
http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide
http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#FLUSH
-r
See also :
http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
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