Storage Layout For Oracle on ASM - One Diskgroup for All? (1212 Views)
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Honored Contributor
Alzhy
Posts: 4,373
Registered: ‎01-22-2002
Message 1 of 11 (1,212 Views)

Storage Layout For Oracle on ASM - One Diskgroup for All?

We've been on ASM storage (all RAID1, cache centric SAN Array - Hitachi Technology) since HP-UX. And our DBs have been configured to use just one ASM Diskgroup to serve all storage needs -- index, redo, temp table spaces and regular table spaces.

Lately - I have been questioning about such a layout. Since there will undoubtedly tablespaces that are more hot and active than the others -- would there hyperactivity somewhat curtail performance on the other tablesapces considering under ASM -- everything is stiped accross the same set of disks?

Would it have been better to have seprate ASM Diskgroups -- say for redos and indexes, temp table spaces and high I/O requirement data (on Flash or faster storage) and all the rest on normal wide striped diskgroups?

Our typical DBases are provisioned with anywhere between 80 to 160 50 to 100 GB disks and everytime space is needed, that adds to the "width" of the ASM stripe and induces +ASM to balance out the database data accross.

In a RAW or Cooked storage environment - an Admin/DBA is given leeway in locating and storing tablespaces on appropirate disks but on a single diskgroup ASM stored DB -- there's not much choice.

Thoughts?
Hakuna Matata.
Exalted Contributor
Steven E. Protter
Posts: 33,806
Registered: ‎08-15-2002
Message 2 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

Shalom,

Best way, cooked or raw is to group by database instance or supported application.

Having the containers be meaningful makes it easier to deal with issues.

A big disk pot becomes the 800 ton gorilla that everybody is afraid to try and move.

SEP
Steven E Protter
Owner of ISN Corporation
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Honored Contributor
Alzhy
Posts: 4,373
Registered: ‎01-22-2002
Message 3 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

Shalom.... question is with ASM - not on raw/cooked storage which is a dead issue as Oracle these days seem to be recommending ASM (and personally -- as a "crossOver Admin" it is wonderful)

But I do now see most SAP implementations and best practices even recommends up to 5 Di+ASM diskgroups...

Hakuna Matata.
Frequent Advisor
Reiner  Rottmann
Posts: 44
Registered: ‎03-10-2011
Message 4 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

You should also put into consideration, how many disc spindles you will need to get the needed performance for your storage.

Also some storage systems will have seperate IO queues per exported LUN. So your target box may have better performance when combining several smaller LUNs via volume manager of the operating system (maybe even with striping!?).
Honored Contributor
Alzhy
Posts: 4,373
Registered: ‎01-22-2002
Message 5 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

Precisely amigo...

Lumping all kinds of Oracle data in one superwide stripe (handled by ASM) I don;t think is a good idea - specially for VLDBs.

I am recommending at least 3 ASM Diskgroups. One for Mainstream Datafiles on normal SAN RAID1 LUNs. Another for super hot and I/O intensive ASM Diskgroup for redo logs, temp table spaces and sort areas - on faster disks or even SSDs and a 3rd for IDX, Conrol files, etc.

Thanks!
Hakuna Matata.
Honored Contributor
TwoProc
Posts: 2,202
Registered: ‎01-11-1999
Message 6 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

For these very reasons - I still don't subscribe to the few luns theory, I still prefer and use the "lotsa luns" theory. Although my lun sizes are much, much larger than they used to be, I have about 50 luns to cover 5 TB usable space on my Hitachi (XP) storage server.
"[That boy] is about as sharp as a sack of wet mice" - Foghorn Leghorn
Honored Contributor
Alzhy
Posts: 4,373
Registered: ‎01-22-2002
Message 7 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

Hey TP.. how many DiskGroups though if you're ASM leaning already?

Lotsa luns (LDEVs) here too. 50 to 100 GB each (Open-Vs and XP/Hitachi too obviously) and my current DBs range in size from 4 to 12 TB.
Hakuna Matata.
Honored Contributor
TwoProc
Posts: 2,202
Registered: ‎01-11-1999
Message 8 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

Alzy, not using ASM - which is an important point. However, where I believe the rubber hits the road is that each lun gets its own scsi queue. I can't imagine that having all of your data jammed down a single scsi queue is a good idea. Ditto for what goes on inside the storage server, what mechanisms are in place to handle each lun there? Wouldn't that be a queue as well? Just my thoughts on this.
"[That boy] is about as sharp as a sack of wet mice" - Foghorn Leghorn
Honored Contributor
Alzhy
Posts: 4,373
Registered: ‎01-22-2002
Message 9 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

TP I am not subscribing to a single large LUN with a very deep Q setting either although my tests with EVAs show they can round circles around a widely striped XP configuration. I've done ORION and IOZone tests pitting 24 XP ldevs accross 4 CHiPs and ACPs (if you're familiar with the tecnhnology) against a 400GB single VDISK from an EVA8400 with 240 DIsks - and the EVA stored DB smokes the XP by a mile. Both used ASM. OE used is Linux. For the EVA test, quueue depth settings I've set to 128. Defaults (32) for XP. YMMV with my comparo though as the EVA was practically

ASM stripes great I believe but only up to a certain "width". ANd I bleieve lumping all hot, warm and superhot datafiles in one ASM Diskgroup is a bad thing.
Hakuna Matata.
Honored Contributor
TwoProc
Posts: 2,202
Registered: ‎01-11-1999
Message 10 of 11 (1,212 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

Nice info on the tests. I like it. However, was that test for throughput, or concurrency? What I've seen on XP systems, is that they never were the hottest throughput engines out there for large single processes, but their total throughput with huge amounts of concurrency diminished far less than anything else I've seen, though I've not tested against EVAs.
"[That boy] is about as sharp as a sack of wet mice" - Foghorn Leghorn
Honored Contributor
Jean-Luc Oudart
Posts: 1,461
Registered: ‎03-10-1998
Message 11 of 11 (1,206 Views)

Re: Storage Layout For Oracle on ASM - One Diskgroup for All?

Hi

The Oracle philosophy is that SAME will remove all your Hot spots issues.
And also that 2 diskgoups one for the FRA and one for the rest is simple and enough to manage your database.

see slide #13
http://www.dbaexpert.com/blog/wp-content/uploads/2009/08/doug-top-10-asm-questions.pdf

Of course if you have different type of storage (ie SSD) you may introduce extra Diskgroups.
This seems quite simplistic and may not be the right answer for all configuration.

Regards
Jean-Luc
fiat lux
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