Re: Does RAID 5 contradict and minimize the benefit of OFA on NT?

Sybrand:

Thanks for quick and helpful reply.

I had thought that mirroring the redo logs on separate disks would avoid problems if one memeber of a redo log is corrupted. How would I avoid this problem : in my configuration, I beleive I should place the redo log memebers on disk 1, 4 and disk5.

Your reply on not putting critical file on RAID 5 devices would lead me to have in my configuration(not the actual drive letters to be used):

Drive a) if this is to be raid 5, I should keep my system tablespace on disk d or disk e. If I have disk a set up for RAId 1 I would be ok?

If disk a,b c, d and e or disk b,c ,d,e are raid 5 enabled, where do I spread out the control files-- on which drives?

Thanks again for the very helpful response. Unfortunately, translating dutch would be an eternity for me.

David Spaisman

Sybrand Bakker wrote in message
<954531184.21961.0.pluto.d4ee154e_at_news.demon.nl>...
>Answers embedded
>david spaisman <david.spaisman_at_compaq.com> wrote in message
>news:8c2sr8$55r$1_at_mailint03.im.hou.compaq.com...
>> Hello:
>>
>> I am working on Oracle 8.0.5 application on NT 4.0. We are in the process
>of
>> setting up a user acceptance server and a development server and have the
>> luxury of having as many disk servers as needed on each respective
>> server(within reason).
>>
>> I am thinking of going with a configuration of drives consisting of the
>> following:
>>
>> a) Oracle executibles, redo log group members, control file, system
>> tablespace
>> b) data files, user files, control file, redo log members
>> c) index files, control file, redo log members
>> d) rollback segments, export files, backup files
>> e) archive log files.
>>
>> Hopefully this configuration will be with physically separate drives and
>> more than one controller If these are logically partitioned drives, I
>> believe it will still depend on how many physical drives and controllers
>> are involved. THanks.
>>
>> David Spaisman
>>
>>
>> However, I have been told that RAID 5 will reduce or contradict the
>> ebenfits purportedly gained from the multiple disk drive/OFA
>configuration.
>>
>> 1) Has any one found this to be true?
>>
>Yes, basically you really can't distribute your data as all your logical
>volumes are spread out on several physical volumes. If you dedicate 1 RAID
>disk to indexes, your indexes will still show everywhere.
>
>
>> 2) Will the benefit of RAID 5 -- faster reads versus slower writes --
for
>a
>> transactonal database still apply?
>>
>No, RAID 5 will hurt performance and cause bottlenecks especially for files
>being sequentially written only, like redo log files. Your setup with
>redolog files on disks with tablespaces is likely to result in performance
>hits.
>> 3) Has any one seen Oracle position on the value OFA versus the benefit
>of
>> RAID 5?
>>
>No, though the consensus in this group is : use a combination of RAID0+1
and
>RAID-5, do NOT place critical files on RAID-5 devices.
>A recent article in the Dutch Oracle Magazine Optimize summarizes as
>follows.
>If your database has less than 50 users and/or less than 250 OLTP
>transactions per minute there should be no objection against RAID5. If one
>of these parameters is exceeded and/or you are running more databases on
one
>server, you should consider using other disks.
>The article discusses heavy OLTP environments, I'm not sure whether you
need
>that, and it will be a hell of a lot of work to translate from Dutch to
>English.
>
>Hth,
>
>Sybrand Bakker, Oracle DBA
>
>> 4) Any other information concerning this situation will be greatly
>> appreciated.
>>
>> Thanks.
>>
>> David Spaisman
>>
>>
>>
>>
>
>
Received on Fri Mar 31 2000 - 14:00:00 CST