Vinum performance

[Greg 'groggy' Lehey]

On Tuesday, 19 August 2003 at  9:56:13 +0200, Niklas Saers Mailinglistaccount wrote:
> Hi all,
> I was wondering if anyone can tell me about their experience of Vinum and
> its performance on RAID5 systems? I've built a vinum-raid of 4 160Gb disks
> that each do a dd if=/dev/zero of=/dev/adNd of about 60Mb/sec. However,
> when I've set up my raid, performance drops to 6Mb/sec, and with only
> three disks it drops to 4.5Mb/sec. Is this usual? 

No.  You should expect about ¼ the write performance of a single disk
under these rather contrived circumstances.

> Because with this speed I cannot run the system at all.

Have you built this system for writing single sectors to a volume
using dd?

> Any good way of tuning the system?

There are some ideas in the man page and the web site.  But in
general, RAID-5 isn't designed for heavy write accesses.

Greg
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