[OpenIndiana-discuss] write speeds faster with no ZIL and L2ARC

[Chris Mosetick]

Lucas, thank you for your ideas. For over a week I looked at the entirety of
iostat's output, including asvc_t, %b, %w as you have suggested. Nothing in
the output seems to be able to explain the transfer speed slowness we
started experiencing. I'm also completely aware that I can keep adding log
and cache devices to a single pool. Doing so ignores the truth of the
matter. Things were humming along just fine with the two X25-E's as log and
cache, and now things move faster without them configured. I'm pretty sure
that ZFS is supposed to move at reasonable speeds when on 7200rpm SATA
disks, and move even faster when low latency log and cache devices are
configured. At least that's how it has been for me.

On Sat, Jun 25, 2011 at 3:53 PM, Lucas Van Tol <catseyev9 at hotmail.com>wrote:

>
> You might want to look at the a_svct and %w  / %b times on iostat -xn 1 ;
> The a_svct should be very low on the intel SSD's; preferably less than one.
> You might also want to look with only one of the SSD's working at a time;
> either ARC or ZIL.
>
> Offhand; this sounds a bit odd, especially since a single set of 12 disks
> in raidz2 isn't particularly fast.
> If your F40 is actually honoring cache flushes as expected; it would not
> actually have very fast random IO due to being MLC drive; the X25-e may
> still be faster.
> Perhaps putting one or 2 of the F40's as cache; and one/two of the x25-e's
> as logs might work better?
> If you have the internal slots and hardware to spare; you can add multiple
> log/cache devices to a single pool.
>
> -Lucas Van Tol
>