ZFS prefetch problem

[Bob Friesenhahn]

On Thu, 31 Dec 2009, jhell wrote:
>> 
>> looks good.
>> tested on 8-STABLE amd64, with/without log/cache ssd. (but not with 
>> zil_disable)
>> 
>
> Thanks for the heads up on this. I have applied the following to a stable/7 
> system @r201336 "The obrien new year copyright ;)" and will write back with 
> further results.

Now if someone can figure out how to crank up (double) the prefetch 
rate for my little test, I would be happy.  145MB/second is not nearly 
enough, especially if zfs can sometimes deliver 5X (or more) that 
rate.

The read performance I see here (under Solaris 10) is very similar to 
the numbers posted by Mickaël Maillot.  In fact initial read 
performance values posted by many others was almost the same, 
regardless of how many drives are available (e.g. 2 or 48 SAS drives). 
This suggests that zfs is not accellerating prefetch fast enough to 
make much difference for 8GB files.

Bob
--
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/