[ILUG] Good Linux SATA RAID Controller
smulcahy at atlanticlinux.ie
Thu Oct 1 08:44:04 IST 2009
Thanks for that. So I normally just look at the "sequential output -
block" as the write speed and the "sequential input - block" as the read
speed. It works for a high level comparison of different devices (but
feedback on the validity of this welcome, and I know all benchmarks can
be gamed so I wouldn't necessarily trust those numbers coming from a
vendors "benchmarking team" - they probably cool the drives to near 0
with liquid nitrogen and do the actual test runs in a low G environment
using only the outer 10 % of each platter).
But back to the 3ware! So the write speed is about 31.5 MB/sec and the
read speed is about 119 MB/sec. For comparison, my 3rd old 5400rpm
laptop drive gives me a write speed of about 29 MB/sec and a read speed
of about 36 MB/sec.
Looking at some other 3yr old systems with newer 1TB drives - using the
disks as plain old disks, I get write speed of about 54MB/sec and read
speed of 76 MB/sec. The same type of system using Linux Software RAID in
RAID1 config gives write speed of 36 MB/sec and read speed of 72 MB/sec.
Finally, looking at a system we purchased this year (not top of the line
or anything, but obviously a newer I/O controller than the previously
mentioned machines) with 1TB drives used as plain old disks, we see
write speeds of 81 MB/sec and read speeds of 93 MB/sec.
So, in a vague handy-wavey type conclusion without going into what kind
of disks you have, what filesystems you are using and what kind of
machine it's all installed in - it looks like the 3ware has pretty good
read speed (which you'd expect if it's smart enough to do reads from
both drives) but pretty poor write speed, relatively. It'd be
interesting to see equivalent bonnie results if you switched the drives
to software RAID (it'd be interesting to see results from my 1yr old
machine using RAID aswell - but probably like yourself, I have only
limited time for testing these things).
Like I said, it'd be interesting to pull these data points together for
a general guide to what kind of performance you can expect with
different configs (I might do so at http://atlanticlinux.ie/blog/ at
> On Tue, Sep 29, 2009 at 12:18 PM, stephen mulcahy
> <smulcahy at atlanticlinux.ie> wrote:
>> To ensure we're comparing the same thing, I normally run bonnie++ with a
>> file size of (physical memory x 2) and leave everything else at defaults.
> This is the test i did on the cheapest 3ware card (2 drives RAID1):
> lucifer:~# bonnie++ -n 0 -u 0 -r 1024 -s 20480 -f -b -d /mnt/xen
> Using uid:0, gid:0.
> Writing intelligently...done
> Reading intelligently...done
> start 'em...done...done...done...
> Version 1.03d ------Sequential Output------ --Sequential Input- --Random-
> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
> lucifer 20G 32303 6 24380 1 121701 2 119.4 0
Stephen Mulcahy Atlantic Linux http://www.atlanticlinux.ie
Registered in Ireland, no. 376591 (144 Ros Caoin, Roscam, Galway)
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