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Performance Difference between logical volumes

Karl_
Frequent Advisor

Performance Difference between logical volumes

Hi,

I am about to install SAP ECC5 in our server. I'm just wondering if there is an effect in performance if I create 1 big /oracle logical volume rather than creating separate logical volumes for sapdata1, sapdata2, etc.

What are the pros and cons of having 1 logical volume for the whole /oracle directory?

Thanks,

Karl
6 REPLIES
RAC_1
Honored Contributor

Re: Performance Difference between logical volumes

Oracle is better with SAME(Strip all mirror everything). Als the manageability is important. I always prefer seperate lvols for data, binaries, archive/redo logs.

So the advantages far outwiegh the disadvantages. You shuold have multiple lvols rather than having just one big lvol.
There is no substitute to HARDWORK
Frank de Vries
Respected Contributor

Re: Performance Difference between logical volumes

For many years the convention was to have seperate lvols and spread i/o over seperate disks.
However , since most of us have SAN on huge
diskstorage cabinets who have the capability
to buffer gigabytes of read and write ,
the whole principle becomes questionable,
as it does not matter.

So if your db is on local disks or on an
attached diskcluster via scsi , definitely
spread lvols.

If you are attached to a SAN it doesn't matter anymore for performance.
Still I would choose for
the old convention as it is more clear
and manageable.

Look before you leap
Jakes Louw
Trusted Contributor

Re: Performance Difference between logical volumes

However, be careful. Some arrays allocate cache per LUN, so a big sequential I/O to an LVOL that is simply a linear collection of LUNs will probably causse a bottleneck at the array ("priority destage" on EMC). If you go for large monolithic LVOLs, then use distributed striping within a PVG.

vgcreate -g PVGstriped -n name disk1 disk2 ..
lvcreate -D y -g PVGstriped etc

Forgive me if my command syntax isn't perfect: been on Solaris for 2 years now, working from memory....:->
Trying is the first step to failure - Homer Simpson
Geoff Wild
Honored Contributor

Re: Performance Difference between logical volumes

I split mine - 1.5 TB across 12 sapdata lvols...more for admin reasons then performance.

Makes it easier to check performance of certain areas (by lvol).

Rgds...Geoff

Proverbs 3:5,6 Trust in the Lord with all your heart and lean not on your own understanding; in all your ways acknowledge him, and he will make all your paths straight.
Yogeeraj_1
Honored Contributor

Re: Performance Difference between logical volumes

hi,

if you are using one of the state-of-the-art SAN, it really does not matter. You would then create lvols as per your convenience and perceive ease..

of course, they are principles that you can adopt as per where to locate your datafiles. (eg. archived regolog, redologs, etc)

hope this helps too!
kind regards
yogeeraj
No person was ever honoured for what he received. Honour has been the reward for what he gave (clavin coolidge)
Eric Antunes
Honored Contributor

Re: Performance Difference between logical volumes

Hi Karl,

At least one lvol for datafiles and redologs/archivelogs and another for binary files and redologs/archivelogs. Redologs/archivelogs should be multiplexed.

Also very important is to have at least 2 tablespaces for each application module: ARD and ARX for Receivables, APD and APX for Payables, etc...

Best Regards,

Eric Antunes
Each and every day is a good day to learn.