topic Re: Performance Difference between logical volumes in Operating System - HP-UX

Performance Difference between logical volumes

Karl_ — Thu, 26 Jan 2006 23:41:13 GMT

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

Re: Performance Difference between logical volumes

RAC_1 — Thu, 26 Jan 2006 23:50:23 GMT

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.

Re: Performance Difference between logical volumes

Frank de Vries — Fri, 27 Jan 2006 02:39:43 GMT

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.

Re: Performance Difference between logical volumes

Jakes Louw — Fri, 27 Jan 2006 03:16:12 GMT

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....:->

Re: Performance Difference between logical volumes

Geoff Wild — Fri, 27 Jan 2006 03:22:22 GMT

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

Re: Performance Difference between logical volumes

Yogeeraj_1 — Fri, 27 Jan 2006 04:17:51 GMT

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

Re: Performance Difference between logical volumes

Eric Antunes — Fri, 27 Jan 2006 05:25:36 GMT

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