Veritas Performance...
2007-12-24 19:19:00
1 Simple question, followed by the background info..
Q) Does veritas write data out to disks in a mirror in serial or
parallel. My benchmarking seems to indicate serial, whereas I think
parallel would be better? Is this tunable somehow?
Background:
I have a Sun E450, currently doing absolutely nothing. I have 2 spare
18G sun disks, on seperate controllers. I've configured them as a
mirrored volume using veritas.
I'm using "iozone" to for benchmarking.
In all my test cases, read performace is reasonable, it varies between
5-15ms, from the volume.
Write performance varies between roughly acceptable (70ms), and shocking
(700+ms).
The 70ms writes happen when I use a fairly large write site, 32K. The
individual disks (vxstat -d) have have write times of about 30ms,
indicating to me that the disk writes are being written sequentially,
which strikes me as suboptimal!
If I use small writes, 2K, then the performace drops through the floor,
individual disk write time is around 150ms, and the volume average is up
around 700+ms. Even doing serial writes out to the disks, I'd expect a
2x-3x slowdown from disks to mirrored volumes, not 5x-6x... Is all that
extra overhead just veritas, or am I missing something?
I understand that lots of small writes are badly inneficient, and this
is not even close to a realistic workload... The 32K writes are closer
to our expected behaviour, I just wanted to see how things went if I
abused
it totally :-)
Thanks all
T.
--
-=*=-=*=--=*=-=*=-=*=-
Tristan Ball
System Administrator
Vision Systems
ph 03 9211 7064
-=*=-=*=--=*=-=*=-=*=-
Comments
Got something to say?
You must be logged in to post a comment.
