Re: Redo log & RAID

I'm a newbie and just finished the Backup and Recovery course for Oracle. My instructor (DBA for Intuit 13+ yrs) was saying the same thing about creating a third or more member in the groups each member stored on a diferent disk (or medium) as software mirroring. For a while I couldn't understand the need for software RAID as I assumed you would mirror your first drive and stripe the first and second on the third and fourth for greater protection. I wasn't realizing that each member of a group was a mirror of the first member stored on their own disks. My question then becomes, if you are mirroring with the software why mirror with the hardware? Wouldn't that become more troublesome. Why do both if one is sufficient and even better? Or is it?

                HardDrive1      HardDrive2     HardDrive3      HardDrive4
                Member a        Member b       Member c
Group 1    redo01a.log     redo01b.log     redo01c.log
Group 2    redo02a.log     redo02b.log     redo02c.log
Group 3    redo03a.log     redo03b.log     redo03c.log

TMAN wrote:

> Okay, I've read all the others so I'll throw in my 2 bits. Here we use a
> combination of oracle mirroring and hw mirroring. The HW is done by and
> EMC 8730 frame so it handles the M1-M2 stuff, and it does diags against
> the disks, calling EMC if either disk starts having problems. Also if one
> or the other has an issue it takes it off line and only uses the good disk
> until the bad one is replaced. We also mirror at the oracle level and to
> make things fast we stripe at the OS level across 4 disks. Oh, yeah, we
> only use raw devices. Is this overkill, possible, do I sleep better,
> definately. Is there a performance hit, don't think so, I see no wait
> events indicating performance issues.
>
> Thom Crider
> Senior DBA
>
> Roger Menhennett wrote:
>
> > Oracle mirrors its redo logs with multiple members per redo log group,
> > advisedly
> > with each member on a separate disk. Question: is HW or SW mirroring a
> > better alternative to Oracle's mirroring of these files?
Received on Wed Apr 11 2001 - 15:35:27 CDT