Re: Oracle and Raid5

>I have a new raid5 system, and i asked myself what is the best logical
>layout
>for the disks.
>Just 1 or diverend logical disks.
>
>Does anyone has experience with Oracle and Raid5.
>

Ron,
It depends on what kind of RAID5 box you have. If it is HP AutoRAID(they have them for NT, I think) then with enough disk capacity you should be OK. The AutoRAID is very intelligent and keeps a mix of RAID0+1 and RAID5. The write working set is kept in RAID0+1. Reads are serviced from RAID5.

If you are not using something like AutoRAID, Keep your redos, and probably TEMP, off of RAID. The parity generation will kill you. Some RAID boxes also have large caches on the controllers and battery backup. A large write delayed cache can help overcome the parity penalty.

If, like AutoRAID, your RAID box stripes data across all disks in the box, you could, in theory, put it all on one logical volume. If your RAID box groups disk, you could create groups that do not share disks and have a much more conventional job of logical layout.

If you have multiple SCSI controllers going to the box and your OS allows you to assign a controller as primary to a volume. Create two volumes each with a different controller. Then split tables and indexes across the two controllers.

Another thing to keep in mind if you decide to put everything into one large logical volume is what to do if you ever need to restore to a conventional JBOD situation. If you have a 10 or 20 GB logical volume on the RAID box, how would you restore this to a bunch of smaller disks? Have a disaster plan that is workable.

I have a 7.3.3 and 7.3.4 instances running under HP-UX with AutoRAID. The 7.3.3 has redos on the RAID, but SYSTEM, TEMP and TOOLS are on a single fixed DISK. On the 7.3.4 instance, I have everything on AutoRAID. Both machines are very FAST.

--
Ken Walters
kwalters_at_pbs.org
DBA
Public Braodcasting Service
kwalters_at_pbs.org Received on Wed Sep 16 1998 - 09:51:16 CDT