Re: RAID experience/recommendations

In article <SEKaeAAwB0s0Mw6r_at_camk.demon.co.uk>, Andy Hardy wrote:

Redo logs are written sequentially. If possible, it is better to keep them away from your other datafiles which are written randomly and thus keep the disk head away from where you would like it to be (i.e. the disk head must keep returning to the last point written in the Redo).

Ideally, Redo mirrored by Oracle on 2 separate 'ordinary' drives is my prefered choice. I have also found that triplicating Redo logs across 3 drives is 20% slower that duplicating (but I don't know why yet).

Raid 0+1 is the best (stripe+each disk mirrored) if you can afford it, but you have a 50% disk redundancy.
Raid-5 gives a 33-20%-ish redundancy but is considerably slower - especially should you lose a drive and have to re-sync the raid set on-line.

You pays your money, you takes your choice.

regs

Neil Chandler

>In article <19980107021500.VAA17428_at_ladder02.news.aol.com>, BRAJB
><brajb_at_aol.com> writes
>>I don't remember if there is a white paper or not, but we are using HP 0+1 in
>>our information warehouse and will be in a few weeks implementing it on our
>>transaction system. The key concepts that have driven home for me are the
>>following:
>>
>>1. Hardware stripe not software
>>2. Redo logs on other that stripe set, ours are on the internal system disk.
>>
>>Hope this helps.
>Why the second?
>
>Andy
>--
>Andy Hardy
>Senior IT Systems Engineer
>Cegelec AEG
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Opinions are mine and do not necessarily reflect those of Cegelec AEG
Received on Thu Jan 08 1998 - 00:00:00 CST