On 5/24/2010 2:48 PM, Thomas Burgess wrote:
I recently got a new SSD (ocz vertex LE 50gb)
It seems to work really well as a ZIL performance wise. My question
is, how safe is it? I know it doesn't have a supercap so lets' say
dataloss occurs....is it just dataloss or is it pool loss?
ZFS is always consistent on-disk, by design. Loss of the ZIL will result
in loss of the data in the ZIL which hasn't been flushed out to the hard
drives, but otherwise, the data on the hard drives is consistent and
uncorrupted.
also, does the fact that i have a UPS matter?
It avoids the scenario of losing data in your ZIL due to power loss
(and, of course, the rest of your system). So, yes, if you actually
care about your system, I'd recommend at least a minimal UPS to allow
for quick shutdown after a power loss.
the numbers i'm seeing are really nice....these are some nfs tar times
before zil:
real 2m21.498s
user 0m5.756s
sys 0m8.690s
real 2m23.870s
user 0m5.756s
sys 0m8.739s
and these are the same ones after.
real 0m32.739s
user 0m5.708s
sys 0m8.515s
real 0m35.580s
user 0m5.707s
sys 0m8.526s
I also sliced it....i have 16 gb ram so i used a 9 gb slice for zil
and the rest for L2ARC
this is for a single 10 drive raidz2 vdev so far....i'm really
impressed with the performance gains
That's going to pretty much be the best-case use for the ZIL - NFS
writes being synchronous. Of course, using the rest of the SSD for
L2ARC is likely to be almost (if not more) helpful for performance for a
wider variety of actions.
--
Erik Trimble
Java System Support
Mailstop: usca22-123
Phone: x17195
Santa Clara, CA
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