On Aug 4, 2010, at 12:26 AM, Richard Elling wrote:
The tipping point for the change in the first fit/best fit
allocation algorithm is
now 96%. Previously, it was 70%. Since you don't specify which OS,
build,
or zpool version, I'll assume you are on something modern.
I'm running Solaris 10 10/09 s10x_u8wos_08a, ZFS Pool version 15.
NB, "zdb -m" will show the pool's metaslab allocations. If there are
no 100%
free metaslabs, then it is a clue that the allocator might be
working extra hard.
On the first two VDEVs there are no allocations 100% free (most are
nearly full)... The two newer ones, however, do have several
allocations of 128GB each, 100% free.
If I understand correctly in that scenario the allocator will work
extra, is that correct?
OK, so how long are they waiting? Try "iostat -zxCn" and look at the
asvc_t column. This will show how the disk is performing, though it
won't show the performance delivered by the file system to the
application. To measure the latter, try "fsstat zfs" (assuming you
are
on a Solaris distro)
Checking with iostat, I noticed the average wait time to be between
40ms and 50ms for all disks. Which doesn't seem too bad.
And this is the output of fsstat:
# fsstat zfs
new name name attr attr lookup rddir read read write write
file remov chng get set ops ops ops bytes ops bytes
3.26M 1.34M 3.22M 161M 13.4M 1.36G 9.6M 10.5M 899G 22.0M 625G zfs
However I did have CPU spikes at 100% where the kernel was taking all
cpu time.
I have reduced my zfs_arc_max parameter as it seemed the applications
were struggling for RAM and things are looking better now
Thanks for your time,
Eduardo Bragatto.
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