Re: Oracle and Raid5

Yes, you are correct. Not sure what the previous poster was thinking, but the loss of one drive in a RAID5 set will NOT cause the loss of your db - that's the whole point of RAID5 in the first place. A hot swap, IMHO, is so cheap you shouldn't be without one.

As for your question, I've worked on three sites which have used RAID5 with some (not all) of their Oracle db's, including my current site. Two of those sites have had disk failures, and on both occasions the systems stayed up and running with too much slowdown and the hot-swap drives rebuilt automatically. In both cases, the dead drives were replaced with new drives without service interruption.

MotoX.

Em Pradhan wrote in message <3600AEF1.2913658C_at_dplus.net>...
>Hi
>I have RAID 5 in one of the site and as per RAID 5 vendor if any one of
the drive
>fails you can swap the disk (replace the disk with new disk) provided your
parity
>protection is On. Under this condition data will be written to new disk
>automatically and for time being system will run in degraded mode.
>So far I never found any documentation to prove that . If any one have an
>experience
>that a disk can be pulled out of RAID 5 and put back in with out requiring
any
>configuration
>please let me know.. also if there exists any documentation let me know
pls..
>thanks (TIA)
>
>
>Craig Munday wrote:
>
>> Hi,
>>
>> By the way, if you are running RAID 5 then you will have to
>> consider your recovery requirements. Assume you create
>> one large RAID set to store most of your datafiles. If one
>> drive fails and your hot swap is not available for what ever
>> reason, you will have to restore and recover all datafiles
>> that were on the RAID device. Depending on the size of your
>> database this could take a while.
>>
>> Cheers,
>> Craig Munday.
>>
>> MotoX wrote:
>> >
>> > Ron Wagner wrote in message <6tmdtk$g28$1_at_news.worldonline.nl>...
>> > >Hi,
>> > >
>> > >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.
>> >
>> > Er, I think that was supposed to read 'different logical disks'? That's
the
>> > assumption I'll work on.
>> >
>> > 1. If your db is light on disk activity - especially writes, which
RAID5
>> > tends to be slow at - then dumping the whole lot on one RAID5 LV will
work
>> > fine. We run a few small (under 5 Gig) db's on RAID5 like this without
>> > problems, and have done for years. Make sure you monitor your system
all the
>> > time.
>> >
>> > 2. If your database is disk intensive, especially on writes, then you
might
>> > be best avoiding RAID5 altogether. Do some testing on your adapter to
find
>> > it's true performance, both read and write, for small and large block
sizes,
>> > and for random as well as sequential I/O. Be wary of good write rates
from
>> > cache installed on the adapter, because you'd normally want it set to
>> > write-through to cope with the case of power loss. (A very high-end,
battery
>> > backed adapter might alleviate this problem. It's your call.)
>> >
>> > 3. The two cases above deal with the extremes. You may pick somewhere
in the
>> > middle: some datafiles on RAID5, some not (say TEMP, ROLLBACK, and
redo, for
>> > instance). Again, without knowing the dynamics of your database it's
>> > impossible to tell. Test. Test. And test again. :-)
>> >
>> > One other thing - mirror the control files, and redo logs and run in
>> > archivelog mode, even if you do use RAID5. I've seen sites where people
>> > think RAID technology saves them from everything. It doesn't,
especially
>> > 'finger trouble', where files are deleted accidentally.
>> >
>> > MotoX.
>> >
>> > >
>> > >Does anyone has experience with Oracle and Raid5.
>> > >
>> > >By the way oracle runs on a NT server.
>> > >
>> > >Thanks!
>> > >Ron Wagner
>> > >
>> > >
>> > >
>> > >
>> > >
>> > >
>
>
>
Received on Thu Sep 17 1998 - 02:13:01 CDT