On Sun, 2 Jan 2000, Thomas Waldmann wrote:
> > - for my use (web/email/cgi) why should I choise RAID 5 and not RAID 1 ?
> Always assuming that CPU power and SCSI bus bandwidth is NOT a limiting
> factor:
>
> RAID1, READ: with mutliple parallel reads, you get better values than with
> single disk - but this is difficult to benchmark.
>
http://www.iki.fi/miku/tiotest will address this 'difficult' part
> RAID1, WRITE: you get about same performance as with single disk
>
> RAID5, READ: you will have better read performance than with single disk. The
> more disks you use, the better performance you will have.
>
> RAID5, WRITE: you will have better write performance than with single disk. The
> more disks you use, the better performance you will have. But: you will
> have quite some CPU load, so a fast CPU is good for performance (and if your
> apps also do a high cpu load, better go for a SMP system).
>
> Do not use too many disks in RAID array as this will lead to an increased
> disk failure probability.
>
> Also do not use too many disks on a single SCSI bus, as bus performance will
> limit RAID performance to some maximum. If you have at least 4 fast HDDs on a
> single bus, you should think about if a second bus (or a faster bus, if
> your device support that) maybe will give you additional speed
>
> Thomas
>
In here, i think that with 'performance' Thomas means raw
continuous throughput to and from raid device. Folks who are considering
building a system which is under high transactional load instead of high
throughput load, a seek time will become dominant. In this area
raid1 performs really well (http://www.iki.fi/miku/raid1)
-- Mika <[EMAIL PROTECTED]>
