Hmmm,
wondering about IMHO strange ZFS results ...
X4440: 4x6 2.8GHz cores (Opteron 8439 SE), 64 GB RAM
6x Sun STK RAID INT V1.0 (Hitachi H103012SCSUN146G SAS)
Nevada b124
Started with a simple test using zfs on c1t0d0s0: cd /var/tmp
(1) time sh -c 'mkfile 32g bla ; sync'
0.16u 19.88s 5:04.15 6.5%
(2) time sh -c 'mkfile 32g blabla ; sync'
0.13u 46.41s 5:22.65 14.4%
(3) time sh -c 'mkfile 32g blablabla ; sync'
0.19u 26.88s 5:38.07 8.0%
chmod 644 b*
(4) time dd if=bla of=/dev/null bs=128k
262144+0 records in
262144+0 records out
0.26u 25.34s 6:06.16 6.9%
(5) time dd if=blabla of=/dev/null bs=128k
262144+0 records in
262144+0 records out
0.15u 26.67s 4:46.63 9.3%
(6) time dd if=blablabla of=/dev/null bs=128k
262144+0 records in
262144+0 records out
0.10u 20.56s 0:20.68 99.9%
So 1-3 is more or less expected (~97..108 MB/s write).
However 4-6 looks strange: 89, 114 and 1585 MB/s read!
Since the arc size is ~55+-2GB (at least arcstat.pl says so), I guess (6)
reads from memory completely. Hmm - maybe.
However, I would expect, that when repeating 5-6, 'blablabla' gets replaced
by 'bla' or 'blabla'. But the numbers say, that 'blablabla' is kept in the
cache, since I get almost the same results as in the first run (and zpool
iostat/arcstat.pl show for the blablabla almost no activity at all).
So is this a ZFS bug? Or does the OS some magic here?
2nd)
Never had a Sun STK RAID INT before. Actually my intention was to
create a zpool mirror of sd0 and sd1 for boot and logs, and a 2x2-way
zpool mirror with the 4 remaining disks. However, the controller seems
not to support JBODs :( - which is also bad, since we can't simply put
those disks into another machine with a different controller without
data loss, because the controller seems to use its own format under the
hood. Also the 256MB BBCache seems to be a little bit small for ZIL
even if one would know, how to configure it ...
So what would you recommend? Creating 2 appropriate STK INT arrays
and using both as a single zpool device, i.e. without ZFS mirror devs
and 2nd copies?
Intent workload is MySQL DBs + VBox images wrt. to the 4 disk *mirror,
logs and OS for the 2 disk *mirror, and should also act as a sunray
server (user homes and add. apps are comming from another server via NFS).
Any hints?
Regards,
jel.
--
Otto-von-Guericke University http://www.cs.uni-magdeburg.de/
Department of Computer Science Geb. 29 R 027, Universitaetsplatz 2
39106 Magdeburg, Germany Tel: +49 391 67 12768
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