On Mon, 16 Jul 2012, Edward Ned Harvey wrote:
From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
boun...@opensolaris.org] On Behalf Of Michael Hase
got some strange results, please see
attachements for exact numbers and pool config:
seq write factor seq read factor
MB/sec MB/sec
single 123 1 135 1
raid0 114 1 249 2
mirror 57 0.5 129 1
I agree with you these look wrong. Here is what you should expect:
seq W seq R
single 1.0 1.0
stripe 2.0 2.0
mirror 1.0 2.0
You have three things wrong:
(a) stripe should write 2x
(b) mirror should write 1x
(c) mirror should read 2x
I would have simply said "for some reason your drives are unable to operate
concurrently" but you have the stripe read 2x.
I cannot think of a single reason that the stripe should be able to read 2x,
and the mirror only 1x.
Yes, I think so too. In the meantime I switched the two disks to another
box (hp xw8400, 2 xeon 5150 cpus, 16gb ram). On this machine I did the
previous sas tests. OS is now OpenIndiana 151a (vs OpenSolaris b130
before), the mirror pool was upgraded from version 22 to 28, the raid0
pool newly created. The results look quite different:
seq write factor seq read factor
MB/sec MB/sec
raid0 236 2 330 2.5
mirror 111 1 128 1
Now the raid0 case shows excellent performance, the 330 MB/sec are a bit
on the optimistic side, maybe some arc cache effects (file size 32gb, 16gb
ram). iostat during sequential read shows about 115 MB/sec from each disk,
which is great.
The (really desired) mirror case still has a problem with sequential
reads. sequential writes to the mirror are twice as fast as before, and
show the expected performance for a single disk.
So only one thing left: mirror should read 2x
I suspect the difference is not the hardware, both boxess should have
enough horsepower to easily do sequential reads with way more than 200
MB/sec. In all tests cpu time (user and system) remained quite low. I
think it's an OS issue: OpenSolaris b130 is over 2 years old, OI 151a
dates 11/2011.
Could someone please send me some bonnie++ results for a 2 disk mirror or
a 2x2 disk mirror pool with sata disks?
Michael
--
Michael Hase
http://edition-software.de
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