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RE: SAME technology question .....

From: Sarnowski, Chris <>
Date: Tue, 10 Jun 2003 11:25:20 -0700
Message-ID: <>

I think there's a lot of confusion about SAME. For example, we have a SAN with the disks grouped into 4-disk RAID-5 sets, and volumes striped across all of the sets (well, we have 2 sets of sets). These are presented as LUNs to Veritas, and then built up into a 1 TB logical volume. All of my datafiles are on that one volume. I multiplex the redo logs, control file, and archived redo logs to a smaller volume on separate spindles. There are several other volumes, used for different things (a copy of the Genbank database, for example), but all residing on the same 3 TB or so of spindles.

I/O is not a bottleneck for us. The database activity is 90% reads and 10% writes, so RAID-5 does not seem to be an issue either. I used to have hot spots that moved from disk to disk, and had to move datafiles around. I don't have to do that anymore. hooray.

It works for us. It may not work so well for a smaller database, or one that has higher write activity.

But are we using SAME? According to one recent post on this list, the answer is no because we're not "really" mirroring on RAID-5. According to others we're not using SAME because I've multiplexed off to separate spindles. We don't follow the advice in the SAME paper of using the outer half of the disks for heavily accessed data. Seems to me that defeats one of the biggest benefits to SAME, for us, which is to stop worrying about micromanagement of disk.

Here's my personal feeling about it. SAME, unlike for example relational database theory, is not a theory. It is an empirical method of getting acceptable throughput and dependability of disk I/O with minimal management overhead. If we're not running SAME, then I suppose I could advocate SAREISM (Strip and RAIDify Everything Including Some Multiplexing) or EMOGATADODIWMMO (see sentence above).


> -----Original Message-----
> From: Johnson, Michael [mailto:[EMAIL PROTECTED]
> Sent: Tuesday, June 10, 2003 1:35 PM
> To: Multiple recipients of list ORACLE-L
> Subject: SAME technology question .....
> A couple years ago, Juan Louiza(sp) of Oracle Corporation put
> out a white
> paper regarding SAME (Stripe and Mirror Everything). I
> have read the
> comments from Steve Adams regarding this methodology.
> I am curious if anyone else is or is not using the SAME
> methodology and what
> has been your experience so far.
> Oracle Corporation has locked into this methodology as
> recently one of our
> DBA's reported that they are teaching this in classes, but
> that others have
> not exactly climbed on board. Excluding Oracle employees if
> you could
> respond regarding your thoughts and experiences I would
> greatly appreciate
> it.
> Thanks For Your Time in Advance.

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Author: Sarnowski, Chris

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Received on Tue Jun 10 2003 - 13:25:20 CDT

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