Re: Separate ASM disk group for online redo log files?
Date: Mon, 11 Apr 2011 17:29:25 -0700 (PDT)
Message-ID: <95f99c39-d03f-458e-ad23-ff95d8892414_at_32g2000vbe.googlegroups.com>
On Apr 11, 5:25 pm, mhoys <matthias.h..._at_gmail.com> wrote:
> On Apr 11, 3:55 pm, John Hurley <hurleyjo..._at_yahoo.com> wrote:
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> > Mathias:
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> > > Ok, I've read a lot about ASM recently :-)
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> > > In one of the technical papers from Oracle, they recommend to have
> > > only 2 disk groups: one for the data files, and one for the recovery
> > > files (FRA).
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> > I have 2 disk groups one separate for the online logs and the other
> > one for everything else.
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> > I am NOT using an ASM based flash recovery area ... not using FRA at
> > all. My archive logs go into a cooked file system.
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> > I was getting some really nasty funky problems early on trying to
> > stress test system while using archive log mode going into ASM based
> > FRA. It was a while back ... but I pretty quick immediately decided I
> > really did not want to put all my eggs into the ASM basket.
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> > Disk based rman backups go into a cooked file system as do my archive
> > logs.
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> > If something goes south with ASM and you pretty much lose
> > everything ... and your backups were inside ASM ... what are you going
> > to do?
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> > When using ASM for the database and testing recoveries ... one option
> > ( which really really needs to be tested and documented ) is starting
> > back at the beginning by recreating the ASM disk groups ... ( create
> > diskgroup blah blah blah FORCE ) ... which also means you are then
> > going to restore a controlfile backup next ).
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> Hello John,
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> Interesting idea of using ASM only for the "data" files and a cooked
> file system for the FRA...
> I just realised that we first do a backup on disk and then the backup
> software writes the backup files from disk to tape. That would
> probably be not possible with ASM as file system, anyway.
>
> Matthias
That depend Mathias,
If you are using 11gR2 you can have a separate disk group and create a volume with an ACFS file system. While it "lives" in ASM, it is accessible as a "cooked" file system - and it is expandable while online - even in a cluster. Oracle liked this feature so well, they now sell the clusterware+ASM as a standalone product called CloudFS. and will be the replacement for OCFS2 (OCFS2 is Linux only).
Having FRA or online redo logs on any other OS-level file system would make it much more difficult should you decide to convert to RAC.
These sorts of "problems" are the reason DBA's need to take a few courses in System and SAN administration.
Sometimes Sys Admins need to also use their brains - true story - I was configuring a 10g RAC system which required separate OCR (2 minimum) and VOTING (3 minimum) devices. The smallest LUN the SAN group was carving was 8GB. These 5 devices need only to be about 500M max. So, this really smart SA creates 5 partitions on the same LUN... Does anyone see a problem with this??? Just because you can do a something, does not mean you should do something. BTW, I have seen an array lose a LUN before... just in case you did not get the previous question.... Received on Mon Apr 11 2011 - 19:29:25 CDT