Stephan Bressler wrote:
>>To cope with logwriter writing sequentialy and the archive processes
>>both reading and writing, I used a setup like this:
>>Four or six redolog files (2G each) on a LUN, each made up of a
>>stripeset containing 20 disks, run by veritas direct i/o configured to
>>min. redo io size (512 bytes for solaris). The logs are interleaved on
>>the LUN's, say log 1,5,9,13 on LUN 1, log 2,6,10,14 on LUN 2 .....
>>
>>This kills a myth: redolog on striped disks doesnt work!
>
> Hi,
>
> so you used LUNs each striped across 20 distinct disks using 512 Bytes
> stripe size (that is, a 10k IO hits all 20 disks)?
>
> If so, I'm not surprised that this setup was slow. You generate a huge
> amount of IOs by the OS.
>
> In our benchmarks (~10MB log/sec) we used 16k stripesize across 12 disks,
> which worked very well. The average LGWR batch (redo_size/redo_writes) was
> ~64k (ranges from 2k to 12k).
> I should mention that we used raw devices.
>
> This was the best compromise for that benchmark.
>
> Regards
> Stephan
>
>
Who said it was slow? If there isnt a problem, why fix it.
I will give you that larger stripe sizes *is* better with large
transactions. But can give problems with many small transactions in the
other end. It's all a tradeoff - works fine for this but poor for
another setup.
rgds.
Received on Sun Dec 08 2002 - 08:11:29 CST
