LVM stripping -

[Deepak Seth_1]

Our Envirnment

HPUX 11.0
V2200 16 MB RAM , TONS of SPACE , 3 FIBER ADAPTER
EMC - 1569 USING SAN
POWERPATH
ON-LINE JFS
ORACLE 7.3.4 & 8i

Iam confused between the choice of stripe size. I have gone through almost all the archives on stripe size but still doesn't feel confident in setting the best for me or it may not be relevent. Few questions

1. How can i set a stripe size of > 64 KB as as lvcreate -I option allow only upto 64KB.Few archives suggest setting to 1 MB to have a good performance .


2. i have set up a stripe size of 16KB in few of the DB File systems but don't know how to check any performance differences.

3. What is block striping v/s extend striping . We already have our disk hardware mirrored so i don't need s/w mirroring.

4. Few archives suggest that the gain of choosing a best stripe is very small and it is good to focus on ORACLE SGA size and mounting oracle datafiles FS using online JFS - to bypass buffer cache . We have database sharing the data and index file .Should the mount options exclude indexes just like redo/archive logs .

Pls. suggest and give me your opinion.

NOte : We don;t have any on-goping performance issues but i want to make best use of technology and knowledeg.


thanx/deepak

[Arockia Jegan]

Pretty good setup. Why do u want to setup the stripe size on the volumes? Your EMC drives are setup with stripes. I also have the same kind of setup here. EMC recommended not to setup the stripe size in the OS level. Also EMC says 960KB stripe size will give very good oracle performance.

[Deepak Seth_1]

idea of setting up the striping is make each lvol/fs use multiple disk drives - more spindle better performance . Did it make sense.

[Arockia Jegan]

Setting up stripe is going to increase the performance. But at your case the stripe is already setup in the EMC drives at the hardware level. Am I right? Are you going to again setup the stripes(Volume level) on the striped disks?

[Deepak Seth_1]

EACH EMC disk is of 73 gig and we stripped to 8.8 gig of LUN . Is that what u mean by stripping ?

[Arockia Jegan]

Striping is a series of disks or devices that are shared by multiple objects. Eg. creating raw partition accross 2 or more drives. Basically you are spreading out the data across the multiple drives. your 8.8gb LUN must be curved out from the 73Gig drives with the particular stripe size. That stripe size may differ according to the hardware and application setup. The overall system performance is enhanced by moving the burden of stripe and mirror maintenance from the OS to the EMC.

[Michael Tully]

Hi,

If you have a bunch of 73GB disks and end up with 8.8Gb LUNS, you will already have a form of striping, and it's called hardware striping. You will not gain anything from attempting to stripe at the software level with LVM. Get your EMC representative to explain exactly how they've set this up. It is to your benefit to completely understand your environment.

Michael

[Deepak Seth_1]

So u suggest stripping at EMC level(backend) . Now we to have to do a stripping at lv level since we don't want to mess around with changes at "bin" file level.

So your conclusion is that we either don't need stripping under our present senerio or its need to be done at backend ie at EMC symm.

[Arockia Jegan]

I'm pretty sure that hardware striping is setup in your drive. Generally EMC does this. You can talk with EMC associate and find out that. Hardware striping is better than software striping. Especially when your EMC has lot of cache, hardware striping will be too good.

[Michael Tully]

Hi,

Youe disk setup is already set up for striping at the EMC end. You don't have to do anything other than to build your volume groups/logical volumes/filesystems etc.

My suggestion is to make sure you understand your environment completely. You should also know about whether you have RAID 5 or RAID 1. If you are unsure you should talk with your EMC engineer.

Michael

[Deepak Seth_1]

i just spoke to EMC CE and he says EMC implement harware stripping only in case of Meta voulmes. I have to track our EMC SE and get a white paper on EMC Symm best pratices. Any final suggestions on how should i proceed on the choice of stripping.

[Mihaita Bighiu]

Hi,

Your setup looks OK. Hope your luns belongs o different EMC physical disks.
I will install EMC Work load analyzer. This tool will do all the others fine tunnigs for you (on line in background).

Ask EMC support for more details.

MB