Life's too short ...(Raid 1 sync times)

Life's too short ...(Raid 1 sync times)

[Richard Scobie]

I am in the process of benchmarking a 4 x 250GB on 3ware 7506 to try and
sort out the myriad of options for RAID and XFS, in order to get best
performance for my workload.

I have tested with software RAID5 and have just attempted to do the same
for software RAID 10. Unfortunately, it is going to take 31000 minutes,
or around 21 days to sync this array and I wish to test 3 different
stripe sizes. Is there some way to allow more bandwidth for the sync up?

The RAID 5 took 70 minutes and was allowed up 100MB/s of idle IO
bandwidth - RAID 1 seems to use < 200kB/s.

While I am very pleased with the hardware RAID 10 result (98261kB write,
97148kB read), I would prefer to use software RAID 10 for a few reasons,
if the performance is similar.

Regards,

Richard

Re: Life's too short ...(Raid 1 sync times)

[Jeff Garzik]

Richard Scobie wrote:
> I am in the process of benchmarking a 4 x 250GB on 3ware 7506 to try and
> sort out the myriad of options for RAID and XFS, in order to get best
> performance for my workload.
> 
> I have tested with software RAID5 and have just attempted to do the same
> for software RAID 10. Unfortunately, it is going to take 31000 minutes,
> or around 21 days to sync this array and I wish to test 3 different
> stripe sizes. Is there some way to allow more bandwidth for the sync up?
> 
> The RAID 5 took 70 minutes and was allowed up 100MB/s of idle IO
> bandwidth - RAID 1 seems to use < 200kB/s.
> 
> While I am very pleased with the hardware RAID 10 result (98261kB write,
> 97148kB read), I would prefer to use software RAID 10 for a few reasons,
> if the performance is similar.


The resync speed defaults to "nice and slow" IIRC... There should be 
some procfs tunable to increase the resync speed...

	Jeff

Re: Life's too short ...(Raid 1 sync times)

[Gordon Henderson]

On Mon, 1 Mar 2004, Richard Scobie wrote:

> I have tested with software RAID5 and have just attempted to do the same
> for software RAID 10. Unfortunately, it is going to take 31000 minutes,
> or around 21 days to sync this array and I wish to test 3 different
> stripe sizes. Is there some way to allow more bandwidth for the sync up?

echo 999999 > /proc/sys/dev/raid/speed_limit_max

Gordon

Re: Life's too short ...(Raid 1 sync times)

[Måns Rullgård]

Richard Scobie <richard@sauce.co.nz> writes:

> I am in the process of benchmarking a 4 x 250GB on 3ware 7506 to try and
> sort out the myriad of options for RAID and XFS, in order to get best
> performance for my workload.
>
> I have tested with software RAID5 and have just attempted to do the same
> for software RAID 10. Unfortunately, it is going to take 31000 minutes,
> or around 21 days to sync this array and I wish to test 3 different
> stripe sizes. Is there some way to allow more bandwidth for the sync up?

echo 200000 > /proc/sys/dev/raid/speed_limit_min

It's a known bug.  The resync code is trying to be nice to other IO in
the system, but forgets that it is itself causing lots of IO in the
lower RAID layer.

-- 
Måns Rullgård
mru@kth.se

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