On 5/24/2010 2:48 PM, Thomas Burgess wrote:
I recently got a new SSD (ocz vertex LE 50gb)
Not familiar with that model....
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?
It should just be dataloss -- you'd potentially lose any filesystem
changes made since the last time data was committed to the actual
storage device (not the ZIL.) It still sounds like losing the ZIL is a
bad idea if you really care about data integrity data though.
also, does the fact that i have a UPS matter?
It might! If you can guarantee that the actual drive won't lose power
then you have much more security. *But*, if the drive is powered from
the computer's power supply or internal bus, then you could have an
issue -- power loss to the drive can occur in this situation when the
system reboots, even though the mains still had power available to them
all the time.
(Hmmm... do the typical SATA power plugs from computer power supplies
have power removed when the system takes a full reset? I would not
*think* so, but with software controlled power supplies I'm not 100%
certain. It might be an interesting test to measure the power from some
common power supplies -- as applied to the SATA power connector --
during a system panic or full reset (reboot -p for example). Its
possible that power is supplied continuously to the peripherals even in
the event of this kind of failure.
DDRdrive X1 solves this with an external power brick. I'm not sure what
other storage devices do here.
The supercap solution is nice because it doesn't need the external
power, but can supply power to the media even when the host removes
power from the device itself.
the numbers i'm seeing are really nice....these are some nfs tar times
before zil:
Wow. That's a pretty huge improvement. :-)
- Garrett (newly of Nexenta)
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
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