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Re: Creation of ASM Disk Group on Solaris 10 ?

From: LS Cheng <exriscer_at_gmail.com>
Date: Wed, 11 Jul 2007 07:22:42 +0200
Message-ID: <6e9345580707102222t1acabebch1feed7a754e987ad@mail.gmail.com>


Hi Alex

When you say stripe collision do you mean hardware stripe larger than ASM or the other way round?

For example HW RAID 0 stripe 64K and ASM 128K and 1MB, will that cause collision?

Thanks

--
LSC




On 7/10/07, Alex Gorbachev <ag_at_oracloid.com> wrote:

>
> Once I've got in trouble when striping conflicted with each other.
> It was for redo logs that are striped with fine striping in ASM (128K)
> and this collided with stripe size of underlying volume so that one
> disk was usually a bottleneck. But that's rather an exception.
> I can imagine (and see it "on the paper") it's also possible to have
> collision with other 1 MB stripe size but I haven't experienced that.
>
> On the other hand, I should admit that statement "ASM works best if
> you can avoid striped volumes" is *too* bold perhaps. :)
> I should have said *usually* the best. One reason is that no stripe
> collision would be possible. Another reason is that it's easy to
> provision space to disk group (add/remove disks) providing that all
> disks are the same. With chunks taken from the common RAID pool you
> have all chances to get one LUN from a more loaded pool. Another
> "unfortunate" placement would be to get a chunk from beginning of the
> disks in the pool and another chunks from the end - you would have
> different performance from them but most important it would force disk
> head jump over the whole disk back and force.
>
> Also, I admit that there are arguably different stripe sizes that
> better fit certain IO patterns and that might not fit within two
> standard 128K and 1M stripe sizes so in some rare cases striping
> behind ASM might be appropriate. I've personally seen that 64K stripe
> size was the best for one case where we were able to compare it with
> all others on the real workload. However, this brings additional
> things to keep in mind while provisioning the space and, to some
> extent, defeats the main benefit of ASM - simplified storage
> management.
>
> A very good paper I can point to
>
> http://www.oracle.com/technology/products/database/asm/pdf/take%20the%20guesswork%20out%20of%20db%20tuning%2001-06.pdf
> It has more details and, actually, benchmark there points to even
> slight increase of performance with introduction of hardware striping.
> But those are artificial tests and ideal layout used while in the real
> life storage admins tend to abstract themselves and, of course, DBAs
> from physical layout.
>
>
> On 7/10/07, Randy Johnson <randyjo_at_sbcglobal.net> wrote:
> > Thanks Alex. Can you provide some documentation to support your "no SAN
> > striping" point?
> >
> > -Randy
> >
> >
> > Randy Johnson
> > Sr. Technical Consultant
> > Enkitec, LLP
> >
> > Office ..... 817-255-3580
> > Mobile .... 817-564-6583
> > Email ..... randy.johnson_at_enkitec.com
> >
> >
> > -----Original Message-----
> > From: gorbyx_at_gmail.com [mailto:gorbyx_at_gmail.com] On Behalf Of Alex
> Gorbachev
> > Sent: Monday, July 09, 2007 5:30 PM
> > To: randyjo_at_sbcglobal.net; oracle-l_at_freelists.org
> > Subject: Re: Creation of ASM Disk Group on Solaris 10 ?
> >
> > Good answer for RTFM question Randy.
> > Just a little comment about striping over striping. ASM works best if
> you
> > can avoid striped volumes but, instead, can give separate physical
> spindle
> > as the LUN. This is how it was designed to work.
> > Unfortunately, in real life storage admins often can't be bothered.
> > :-(
> >
> >
> > On 7/9/07, Randy Johnson <randyjo_at_sbcglobal.net> wrote:
> > > Vivek,
> > > This is the kind of question that if you have to ask you are not ready
> > > for the answer. The best advice I could give you is to read Nitin
> > > Vengurlekar's "ASM Best Practices" white paper and refer you to
> > > Oracle's Cluster Ready ServicesInstallation Guide. If you've never
> > > done this before you should brace yourself for some heavy reading.
> > >
> > > In short to answer your questions the raw devices (LUN's) you want to
> > > use for ASM must be shared and visible to all nodes. This is generally
> > > done using HBA (host bus adapter) cards that allow your servers to
> > > "see and interact with" the SAN storage array. There are some
> > > specifics in configuring ASM on Solaris (which slices you can/should
> > > use) and which slice to never use. Regarding commands for SAME. This
> > > is done by having your storage administrator stripe the volumes across
> > several physical devices.
> > > Then you as the DBA come through and configure your ASM volume groups
> > > as a combination of these "striped" LUN's. In other words the LUNS are
> > > striped on the SAN and the ASM Diskgroups provide a second layer of
> > striping.
> > >
> > > -Randy
> > >
> > >
> > >
> > > Randy Johnson
> > > Sr. Technical Consultant
> > > Enkitec, LLP
> > >
> > > Office ..... 817-255-3580
> > > Mobile .... 817-564-6583
> > > Email ..... HYPERLINK
> > > "mailto:randy.johnson_at_enkitec.com"randy.johnson_at_enkitec.com
> > >
> > >
> > >
> > > _____
> > >
> > > From: oracle-l-bounce_at_freelists.org
> > > [mailto:oracle-l-bounce_at_freelists.org]
> > > On Behalf Of VIVEK_SHARMA
> > > Sent: Monday, July 09, 2007 3:09 AM
> > > To: oracle-l_at_freelists.org
> > > Subject: Creation of ASM Disk Group on Solaris 10 ?
> > >
> > >
> > >
> > > Folks
> > >
> > >
> > >
> > > Need to Setup a 2 Instance ASM-RAC Database from scratch for an
> > > internal Test Benchmark.
> > >
> > >
> > >
> > > * What Commands are used to create an External ASM Disk Group on
> > > Solaris 10?
> > >
> > > * Any Additional Solaris Commands to make the SAME Disk Group
> Visible
> > > to BOTH SUN Nodes?
> > >
> > >
> > >
> > > NOTE - Disk Group to use External Hardware RAID (10) provided by the
> > > Storage Box
> > >
> > >
> > >
> > > Oracle 10gR2 on Solaris 10
> > >
> > >
> > >
> > > Any Docs, Links will help
> > >
> > >
> > >
> > > Cheers & Thanks indeed
> > >
> > >
> > >
> > > Vivek
> > >
> > >
> > >
> > >
> > >
> > >
> > >
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> >
> > --
> > Alex Gorbachev, Oracle DBA Brewer, The Pythian Group
> > http://www.pythian.com/blogs/author/alex http://blog.oracloid.com BAAG
> party
> > - www.BattleAgainstAnyGuess.com
> >
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>
> --
> Alex Gorbachev, Oracle DBA Brewer, The Pythian Group
> http://www.pythian.com/blogs/author/alex http://www.oracloid.com
> BAAG party - www.BattleAgainstAnyGuess.com
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>
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Received on Wed Jul 11 2007 - 00:22:42 CDT

Original text of this message

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