zfs discuss - Mar 2010 - How to disable ZIL and benchmark disk speed irresponsibly

I have a system with a bunch of disks, and I?d like to know how much faster
it would be if I had an SSD for the ZIL; however, I don?t have the SSD and I
don?t want to buy one right now.  The reasons are complicated, but it?s not
a cost barrier.  Naturally I can?t do the benchmark right now...

But if I could create a RAM device, and use that for ZIL, of course it would
be irresponsible, but I have no data on the system yet, and this is all just
to establish the upper bound of what performance could be if I had the SSD.
After doing the benchmark, I would reformat the machine anyway.

Can I create a ram device and use it for the ZIL?
Can I somehow disable the ZIL in an irresponsible way, to establish the
upper bound for performance on my system?

Thanks...
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://mail.opensolaris.org/pipermail/zfs-discuss/attachments/20100302/bf203b89/attachment.html>

On Mar 2, 2010, at 12:36 PM, Edward Ned Harvey wrote:
> I have a system with a bunch of disks, and I?d like to know how much faster
it would be if I had an SSD for the ZIL; however, I don?t have the SSD and I
don?t want to buy one right now.  The reasons are complicated, but it?s not a
cost barrier.  Naturally I can?t do the benchmark right now...
> 
> But if I could create a RAM device, and use that for ZIL, of course it
would be irresponsible, but I have no data on the system yet, and this is all
just to establish the upper bound of what performance could be if I had the SSD.
After doing the benchmark, I would reformat the machine anyway.
> 
> Can I create a ram device and use it for the ZIL?
Yes, see ramdiskadm(1m)
> Can I somehow disable the ZIL in an irresponsible way, to establish the
upper bound for performance on my system?
Yes, but performance achieved by disabling the ZIL is always better, so
it seems like an unachievable goal.
 -- richard

ZFS storage and performance consulting at http://www.RichardElling.com
ZFS training on deduplication, NexentaStor, and NAS performance
http://nexenta-atlanta.eventbrite.com (March 16-18, 2010)