RE: What would you do with 8 disks?

Hmmm. Maybe I should not have said first or second as I was quoting directly from the Grid Computing with RAC book cited below, (page 228). There it is phrased 'striping is implemented in the lowest

position...'(01), and then 'mirroring is implemented at the lowest
position...'(10).  I took that to mean the lowest position being
'first'... maybe that was wrong.  If not, then there is a discrepancy.  

Joel Patterson
Database Administrator
904 727-2546

-----Original Message-----
From: Amar Kumar Padhi [mailto:amar.padhi_at_gmail.com] Sent: Wednesday, April 08, 2009 3:40 PM
To: Patterson, Joel
Cc: cicciuxdba_at_gmail.com; david.best_at_gmail.com; oracle-l_at_freelists.org Subject: Re: What would you do with 8 disks?

Hi Joel,
1+0 is mirrored first and then striped.
0+1 is striped first and then mirrored.

RAID 1 is only mirrored disk, and RAID 0 is for stripe only. The above combination would identify the same in that order. Yes RAID 1+0 would perform better in general and when recovering from a failure. Correct me

if I am wrong, or you meant the same.

Thanks!
amar
www.amar-padhi.com

Joel.Patterson_at_crowley.com wrote:
> Geez. I called them wrong. If you read the conclusion you would be
confused. The correct terminology for this is:
>
> 10 is striped first and then mirrored (a striped mirror), and
> 01 is mirrored first and then stripped (a mirrored stripe).
>
>
> Joel Patterson
> Database Administrator
> 904 727-2546
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Joel.Patterson_at_crowley.com
> Sent: Wednesday, April 08, 2009 8:47 AM
> To: cicciuxdba_at_gmail.com; david.best_at_gmail.com
> Cc: oracle-l_at_freelists.org
> Subject: RE: What would you do with 8 disks?
>
>
> I am for RAID 10, and only wish to point out that there is a
difference between 10 and 01. One is a mirrored stripe, and the other is a stripped mirror.
>
> See ABOVE CORRECTION.
> 10 is striped first and then mirrored (a mirrored stripe), and
> 01 is mirrored first and then stripped (a striped mirror).
>
> 01 - Striping is implemented in the lowest position, meaning from a
group of drives. A stripe is formed and then two such stripes are mirrored resulting in a logical drive. (The loss of any drive makes the entire stripe invalid and the stripe is detached from the mirror pair. When the failed disk is replaced, the entire stripe must be brought up to date).
>
> 10 - Mirroring is implemented at the lowest position. A group of
mirrored drives is used to create a stripe. (If a disk fails in a striped mirror layout, only the failing disk is detached, and only that portion of the volume loses redundancy. When the disk is replaced, only a portion of the volume needs to be recovered. Mirrored drives are independent units. When a disk is lost, it affects only one mirrored pair).
>
> Compared to a mirrored-stripe, a striped-mirror offers more tolerance
to disk failure. If a disk failure occurs, the recovery time is shorter for a striped-mirror layout. (Thus 10 is superior to 01).
>
> -- From Oracle 10g Grid & Real Application Clusters, Mike Ault, Madhu
Tumma.
>
> Joel Patterson
> Database Administrator
> 904 727-2546
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Guillermo Alan Bort
> Sent: Wednesday, April 08, 2009 12:06 AM
> To: david.best_at_gmail.com
> Cc: oracle-l
> Subject: Re: What would you do with 8 disks?
>
> If these are 8 external disks, then RAID 0+1 is the best choice (IMHO)
> since you have both performance and redudnacy. RAID5 should only be
> used with SAN boxes, which use it whether you like it or not. and OS
> can be on RAID1 if you need redundancy... I/O on those fs is not
> *that* critical anyway.
>
> hth
> Alan Bort
> Oracle Certified Professional
>
>
>
> On Wed, Apr 8, 2009 at 12:47 AM, dave <david.best_at_gmail.com> wrote:
>
>> Hey all,
>>
>> If you had 8 disks in a server what would you do? From watching this
>> list I can see alot of people using RAID 5 but i'm wary of the
>> performance implicatons. (http://www.miracleas.com/BAARF/)
>>
>> I was thinking maybe RAID 5 (3 disks) for the OS, software and
>> backups. RAID 10 (4 disks + 1 hot spare) for the database files.
>>
>> Any thoughts?
>> --
>> http://www.freelists.org/webpage/oracle-l
>>
>>
>>
>>
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