On Jul 13, 2009, at 2:54 PM, Bob Friesenhahn <bfrie...@simple.dallas.tx.us
> wrote:
On Mon, 13 Jul 2009, Brad Diggs wrote:
You might want to have a look at my blog on filesystem cache
tuning... It will probably help
you to avoid memory contention between the ARC and your apps.
http://www.thezonemanager.com/2009/03/filesystem-cache-optimization.html
Your post makes it sound like there is not a bug in the operating
system. It does not take long to see that there is a bug in the
Solaris 10 operating system. It is not clear if the same bug is
shared by current OpenSolaris since it seems like it has not been
tested.
Solaris 10 U7 reads files that it has not seen before at a constant
rate regardless of the amount of file data it has already read.
When the file is read a second time, the read is 4X or more slower.
If reads were slowing down because the ARC was slow to expunge stale
data, then that would be apparent on the first read pass. However,
the reads are not slowing down in the first read pass. ZFS goes
into the weeds if it has seen a file before but none of the file
data is resident in the ARC.
It is pathetic that a Sun RAID array that I paid $21K for out of my
own life savings is not able to perform better than the cheapo
portable USB drives that I use for backup because of ZFS. This is
making me madder and madder by the minute.
Have you tried limiting the ARC so it doesn't squash the page cache?
Make sure page cache has enough for mmap plus buffers for bouncing
between it and the ARC. I would say 1GB minimum, 2 to be safe.
-Ross
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