Re: Oracle9i - which RAID ??

Wolfgang Blümlhuber wrote:

> Hi,
>
> I'm using Oracle 8.05 on WinNT4.0 WS on DELL Workstation (300 MHz, 768 MB
> RAM
> 3 SCSI Harddisks - no stripeset, no mirror, no RAID)
>
> Now I want to migrate to Oracle 9i on Win2k-Server on a DELL PowerEdge6400
> Machine
> Perc3-RAID5 System with HotSpare (5+1) and 128 MB RAID-Cache.
>
> Oracle recommends to avoid RAID5 for DatabaseFiles and RedoLogFiles.
> On our Database we mostly have long read and write transactions (approx. 1/2
> hour)
>
> What "RAID"-system can you recommend ?
> Do I have lost in performance if I will use RAID 5 ? Or is the gain of
> performance
> marginal if using RAID 0+1 (stripping + shadowing) which is recommended by
> Oracle ??
>
> My intention is to use RAID 5 because of protection against failures.
>
> Does anyone have experiances ???
>
> Thanks in advance.
>
> Wolfgang.
>

The allways good saying is - it depends.

On how many i/o have you need for, and how many of them are reads and how many are writes.
Few writes, many reads then raid 5 is ok. With a 50/50 ratio raid 5 *can* be used if there are few disks in the raid (3-4-5), modify low (update) and peak load is low (<< max disk io/number of disks).
Best is raid 10 (not 01), mirrored lun's striped to a set (10) and not stripes mirrored (01). In the later case, one disk fails - the hole stripe set (one mirror side) is down. Two disks fail (one on each side), the hole set is down. The raid 10 has a lot higher change of protecting the data when disaster strikes.

PS: raid5 is not usable for redologs - sequential writing rules the game here.

rgds

/svend Received on Thu Jun 27 2002 - 11:52:01 CDT