Databases
cancel
Showing results for 
Search instead for 
Did you mean: 

Best LVM partitionning for Oracle

eps67
Occasional Visitor

Best LVM partitionning for Oracle

Hello,

We've got a new EVA 6400 for which I created 8 vdisks for oracle data and 8 vdisks for oracle indexes. These vdisks have been presented to a HP-UX host. I made them known (pvcreate) to LVM creating 16 physical volumes.

Now I have one volume group for oracle data containing one logical volume for 8 physical volumes. And ditto for oracle indexes, one vg containing one lv for 8 pv.

My question is what is the best in matter of IO and queuing :
- my LVM partioning
- 2 vg, one lv for one pv in each vg
- 16 vg, one lv for one pv in each vg
- other ...

Best regards
Laurent
6 REPLIES
Hein van den Heuvel
Honored Contributor

Re: Best LVM partitionning for Oracle


Hmmm,

Laurent, you may want to rethink the whole approach.
Several notions applied seem to stem from the dark ages, before we knew better or could do better.
1) Data - Index separation? Why? To increase your chances of hot spots?
2) Multiple smaller physical volumes combined back into a single VG? Why? To create more complexity
3) What 'real' value is LVM adding? Have you considered ASM ?
4) What will the backup method be? RMAN?
5) Which HPUX version? Does it offer native multipath or do you need to try balance the fibre channel load manually?

Start with Oracle guidelines, not HP guidelines.
After that tweak to match HP's recommendations.

Good Luck!
Hein

Steven E. Protter
Exalted Contributor

Re: Best LVM partitionning for Oracle

Shalom Laurent,

The primary factor in Oracle performance is the configuration of the disk on the EVA prior to presenting it to the HP-UX system.

For heavy write systems, I recommend from experience raid 1 or raid 10 presentation.

For sequential writes like archive logs, raid 5 is sufficient.

Each major disk area, data/index, redo, archive logs should have its own LUN so you can customize configuration.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
eps67
Occasional Visitor

Re: Best LVM partitionning for Oracle

Thanks all.

For Hein :
1)data-index : one of the first rule of OFA is to avoid contention between data and index
2)16 pv of 40Gb is for multiplexing IO and avoid an IO botleneck.
3 & 4)LVM is ok in our case because legacy and backup is file system based and no rman.
5)HP-UX 11.31 Each PV has 8 lunpaths.

For Steven :
Indeed, our vdisks are in raid 1 and each major disk area has its own LUN. Mount options have been well chosen (best practices document)

Everybody :
Perhaps, I'm not clear :
Is multiplexing physically data, index, redo, archivelogs between multiple disks enough ?
For instance, 320 Gb of indexes has been divided into 8 physical volumes of 40 Gb so as to multiplex IO and avoid contention on only one physical volume. Now, what's best in a LVM scenario for these 8 pv :
-1 volume group with 1 logical volume
-1 volume group with 8 logical volumes
-2 volumes group with 4 logical volumes
- ...
What I would like to know : does logical multiplexing inside LVM matters as it matters at a physical level ?

laurent
Terry.giblin
Frequent Advisor

Re: Best LVM partitionning for Oracle

Dear Hein van den Heuvel,

"Several notions applied seem to stem from the dark ages, before we knew better or could do better."

I know what you mean.

A few weeks ago, a unix guru friend called us dinosaur's, when I was discussing VMS with his boss.

But I think, Steven summed it up, in one sentence.

"The primary factor in Oracle performance is the configuration of the disk on the EVA prior to presenting it to the HP-UX system."

Then check your sql's, if I was you.

By the way what are Oracle's and HP's latest guidelines, if you don't mind me asking?.

What have I missed?

Terry Giblin
Terry.giblin
Frequent Advisor

Re: Best LVM partitionning for Oracle

Dear eps67,

However as you have pointed out, by asking a very good question.

We would not be doing your job correctly, if you did make sure the OS and LVM is correctly configured also.

Now apply again the same rules and philosophy except at the OS level.

Then do the same to Oracle, with the help of your friendly DBA.

Terry Giblin




Mark H Stewart
Frequent Visitor

Re: Best LVM partitionning for Oracle

One thing I noticed in this thread that hasn't been emphasized is that trying to separate data and indexes to avoid contention for Oracle is not necessary. Oracle will read all of the index, if it chooses to use an index, then read the all the data. It does not switch back and forth. So you can put your data and indexes on the same volume.
Chance favors the prepared mind. - Louis Pasteur