Re: Laying out Oracle on a SAN
- From: Thomas Roach <troach@xxxxxxxxx>
- To: dcowles@xxxxxxxxxx
- Date: Sat, 6 Feb 2010 19:24:46 -0500
All a matter of preference really. If something like NFS or file system,
then it might be a good idea to separate them into different mount points
for manageability. With 10g and up I make use of the Flash Recovery Area and
store my archivelogs there and I have DG so I don't multiplex the archive
logs on my primary, but multiplexing is a good practice. If these are LUNS
(block devices) I prefer to use ASM with 10g and up since it stripes the
data across all disks within a disk group and that separates the I/O really
well. At my new place, once we went to ASM with uniform block devices (they
were different sizes before) we have the SAN lighting up like a Christmas
tree and I/O performance is great. The issue with ASM is only Oracle knows
about the disk location, but with 11g they now have the ASM file system or
Database File System. I haven't had a chance to play with it but plan on it
within the next few weeks.
BTW at my previous place, we did a POC with Oracle on an IBM z10 Mainframe
running under zlinux and a DS8300 IBM San (supposed to be their top of the
line). Because of the way it was architected, I needed 2TB of storage and
they only allocated disks in 3GB chunks to maximize I/O. I could have gotten
a larger size disk, but then I would only get 1 I/O channel to the disk.
They said it was something about the way Mainframe or "DASD" storage works
and this would give us max throughput (They called it a "Mod-3"). We threw
about 700 Luns into an ASM group and then hammered it. The Mainframe experts
working with us said they had never seen an 8300 light up like that before.
Every disk was being hit pretty evenly (ALL of them) I forget our throughput
but it was saturating the I/O channels (4 of them). After 8 hours,
everything slowed down. The SAN was shot. They had to call support and
replace some components.
I'm an advocate for ASM. Haven't had any issues. If you want to take backups
though, you need to use some SAN Mirroring or RMAN.
Hope this helps.
Tom
On Sat, Feb 6, 2010 at 1:25 AM, Douglas Cowles <dcowles@xxxxxxxxxx> wrote:
>
> Looking for tips as to laying out an Oracle DB on a SAN. I assume you
> probably want the fastest I/O for the redo logs and temp?
> The SAN I am working with has LUNS are carved up out of 10 or so disks on
> RAID5. Does it matter if we put the archive logs and the datafiles on the
> same LUN? Are these kinds of questions better suited to the SAN expert?
> Assuming I can defer a lot to the SAN expert, what I/O requirements and
> path requirements should I provide them? Centralized storage is
> centralized storage so I'm not sure how to parse things out. I also
> realize a lot of this may depend on the kind of SAN and its particular
> characteristics, but are there generic rules that can be provided?
>
> Doug C
--
Thomas Roach
813-404-6066
troach@xxxxxxxxx
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