Re: Need advice on RAID5
Date: 1996/04/02
Message-ID: <1996Apr1.225541.7864_at_venus.gov.bc.ca>#1/1
mew_at_world.std.com (Michael E Willett) wrote:
>RHUZ94A_at_prodigy.com (John Flack) writes:
>>In testing, we had the same good experience - pull a drive, and the
>>database stays up and running, albeit a bit slower. Put in a fresh drive,
>> and after a short while you are back in business as if nothing happened.
>>However, in real life we lost a drive under circumstances (still an
>>unsolved mystery) that caused the hot recovery to fail. At that point,
>>we were forced to repartition and restore the entire RAID from a backup.
>>Then we had to recover the database. We had some missteps in the
>>recovery process because Unix was reporting that some of the file systems
>>on the RAID were good, when actually ALL of the file systems on the RAID
>>needed to be restored.
>What RAID hardware was involved?
>M Willett
>Storage Computer
>http://www.storage.com
The good thing with RAID 5, which I assume you are talking about, is that it addresses the problem of disk failures in a cost effective manner. The problem is that on a small system you are likely to end up with one SCSI controller that has a system disk and several gigs of RAID disk. Which forces the entire data base onto the RAID disk. You think that RAID will protect you, but just let the RAID controller, cabling, or any other single point of failure go bad and you could end up loosing you're entire data base. Just like John Flack or Us.
You need to have a system with a second SCSI controller. The disk on it does not have to be RAID or even Mirrored (but that would be a good idea). This gives you a place to place to save a SECOND copy of the REDO LOGS, ARCHIVE LOGS and CONTROL FILE. Then if your RAID system goes bad and you finally have it repaired, you can recover the data base. That is assuming you've been doing good old tape backups and not fallen into the trap of not doing them since you had RAID.
Don Berryman Berryman_at_Qp1.Qp.Gov.Bc.Ca Queen's Printer BC Mail Plus / Fax Message Centre 563 Superior, 1150 Mackenzie Victoria, BC, Canada Victoria, BC, CanadaVoice: (604) 356-5392 (604) 727-3611
Fax: (604) 387-0388 (604) 952-4049 Received on Tue Apr 02 1996 - 00:00:00 CEST