Re: raid 10 su, sw settings

Justin Piszcz
2007-12-31T19:07:57Z

On Mon, 31 Dec 2007, Brad Langhorst wrote:

>
> On Mon, 2007-12-31 at 12:04 -0500, Justin Piszcz wrote:
>
>>>
>>> Typical blocks/sec from iostat during large file movements is about
>>> 100M/s read and 80M/s write.
>>>
>>
>> #1 What type of performance do you expect with a 4-disk raid10?
>
> Are you saying that i should not expect more?
> I expect about 70% better performance, since I think a single disk
> should be able to do 100M/s. Maybe this is unreasonable?
A single disk may do 90MiB/s burst but not sustained for read or write, at
least not cheap SATA disks and when you get toward the middle part of the
disk the speed wil drop off significantly. 100MiB/s read and 80MiB/s
write for RAID10 sounds about right to me. Maybe someone else on the list
with a similar configuration can chime in with their benchmarks.

>
>
>> #2 You should be able to umount/mount with the new sizes, although I have
>> not tested it myself b/c I typically use sw raid here (sunit/etc is
>> optimized for sw raid).
> I am able to do the remount, but it seems to have had no impact.
> I don't know why but I see 3 possibilities:
> - Perhaps because su/sw settings don't matter very much.
> - maybe it didn't take effect (rebooting this system is not a preferred
> option)
> - maybe it doesn't matter if the partition layout is not optimized.
>
> Brad
>
>