Re: Creation of ASM Disk Group on Solaris 10 ?

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

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>

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