Thank you Thomas and Mertol for your feedback.
I was indeed aiming for the x25-E because of their write performance.
However since these are around 350? for 32 GB I find it disturbing to only use
it for ZIL :-)
I will do some tests with a cheap MLC disk.
I also read about the disk cache needing to be disabled to avoid dataloss after
a powerloss.
If a journaling FS is run over iscsi this should not become an issue right?
( Or will ZFS be affected by missing data from cache? )
Since I am hanging here now:
Do people experience trouble on exporting iscsi zvol's with their cpu-load
because of the TCP-IP calculations?
Or is is safe to ignore the TOE network cards?
Regards,
Armand
----- Original Message -----
From: Thomas Burgess
To: A. Krijgsman
Cc: zfs-discuss@opensolaris.org
Sent: Monday, January 11, 2010 3:02 AM
Subject: Re: [zfs-discuss] ZFS Cache + ZIL on single SSD
Next to that I am reading all kind of performance benefits using seperate
devices
for the ZIL (write) and the Cache (read). I was wondering if I could
share a single SSD between both ZIL and Cache device?
Or is this not recommended?
i asked something similar recently. The answers i got were along these lines:
you can use a single ssd but it's not a great idea. If you DO need to use a
single ssd for such a thing, make sure it's one of the more expensive SLC
variety like the intel x25-e
The MLC variety of SSD works well for L2ARC and is much cheaper (you can pick
up some for less than 100 bucks) while the ZIL really should have the SLC
variety.
I'm not an expert though, i'm just passing on advice i've been given.
For reads and dedup L2ARC does make a dramatic difference, and for NFS and
database stuff an SSD ZIL will make a huge difference.
I've heard of people getting 5-10x's performance increase on reads just by
adding a cheap ssd so i'd say it's worth it if that's the type of dataset you
have.
Another thing i was told on more than one occasion was that you may not even
NEED a ssd for your ZIL (basically you should run a script to see if you need a
ZIL at all, i don't remember where this script is but i'm SURE someone will
reply with it)
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