Best Practice LVM Striping

[KapilRaj]

Folks,

I have 15 *10 GB LUNs (ESS Storage hardware level RAID-5) and need to create 6 filesystems for an oracle 817 database. Which of the following is the best & why.

01. Stripe all the filesystems on to 15 luns.
02. Stripe 2 filesystems each on to 5 luns and have 3 sets of 5 luns this way.

There are two small redologs volumes as well .. I could'nt think of a best method than striping it on all available lun's.

Let me know your views....

Regds,

Kaps

[Steven E. Protter · Accepted solution]

Oracle recommends Raid 1 or Raid 10 for data, index and redo logs.

Neither of your scenarios meets that standard.

If you can not afford to meet Oracle guidelines choose the scenario (01) that puts the data on the maximum number of physical disks possible.

To be certain, you will need to find out how the LUNS have been built on the disk array.

SEP

[RAC_1]

I would go with option 2. Why?? With first option, in case you want to extend a FS, you will have to add 15pvs. (that is because, the lvol created will be stripped across 15 pvs. Looks a management nihtmare to me)

With second option, management will be easy and the same time you are stripping over 5 disks.

Anil

[Alzhy]

Kapil, I really do not know if there are any benfits in further "RAIDing" (RAID-0) your RAID5 LUNS from your shark apart form the fact that you will not have any "hot spot" from glance, sar or iostat monitoring.

My rule of thumb is to stripe the already RAIDed LUNS (RAID5,10,S,etc) N-ways no matter what array I am using. The value of N (or columns) are in multiples of 2 - no less than 4 and no more than 8.

The most host-based important striping parameter is your stripe width or size -- which is dependent on the type of DB you are running. 64Kb seem to be neutral for both OLTP and DSS use although I have built 8-way stripes with up to 1024KB as stripe size and adjusted my Filesystem and VOlume Management tunables to match this structure as well as my DB's needs.

[Victor BERRIDGE]

Hi,
Where do your 15 LUNS come from: from 3 (more or less?) distinct array groups? I tend to stripe across different LUNS from different array group where possible then choosing the primary access in alternance between the different controllers...

All the best
Victor

[KapilRaj]

I will make sure that the set is from diffrent LSS at the storage level. From mgmt point of view it is difficult to manage a stripe set of 15 disks than a 5 disks set. But is there any advantage by adding more disks in the set ? i mean we may end up getting more buffer cache or so ? as we have moire disks now ?

Kaps

[Alzhy]

If your storage payload is a DB instance and it is dual purpose (ie.) OLTP by day and DSS by night -- then I suggest you add another 10G LUN so you have 16. Stripe 8-ways so you have 2 x 80GB volumes to house your instance on. Use a 64KB stripe-width with what ever volume manager you're using - LVM or VxVM..

[Devender Khatana]

Hi Kapil,

I would also go with option2 as there is no point in stripping it across more than 4-5 LUNS where actually your LUN is allready stripped in RAID5 at hardware level.

Here we have got HP's XP1024 and were also running Oracle817 database prior to upgradation last week. We have stripped our Veritas volumes across approx six LUNs and had no problem. (Hardware Level Raid5 with 3D+1P) Same applies to LVM's Logival volumes as well.

HTH,
Devender

[Alzhy]

Just one more thing, please avoid striping N-ways with N being an odd number. Always have your storag columns in multiples of 2.

[Christopher Caldwell]

Oracle and HP's recommendation is "SAME" -- Stripe And Mirror Everything. If you read the paper here:
http://www.oracle.com/technology/tech/hp/storage.pdf

They claim that there's minimal performance advantage gained by separating redo/indexes/data.

As always, YMMV, so you'll probably want to test what's best for you.