strip / mirrored -> performance

[Hannibal_1]

Hi,

I stripped a lvol (extent-based striping, one strip is 1 mb) via 5 disks and after this I mirrored the lvol.

Oracle uses a 8kb blocksize.
Will the performance be better with or without striping?

[MARTINACHE]

Hi,

Strip will certainly increase oracle performances. But I will add some advice :

- Try to put data and indexes on differrent disks.
- If you have online-JFS, you can mount a filesystem with "mincache=direct" option.
- I hope that your 5 disks are not on the same SCSI controller : with more than 4 disks, you get an SCSI controller bottleneck.

Regards,

Patrice.

[Fred Myers]

It actually depends, the amount of a diffrence is mostly minimal but a few questions.
1. What kind of disks are you using.
If it is an enterprise storage solution with a cache on it you will have no difference in speed as the cache will do all the work, actually striping an enterprise solution will make it slower.
2. if you are on different controllers and want to stripe I recomend making the filesystem block size equal or a multiple of the oracle table block size, then stripe with that block size in account.

I 8 block size oracle, 8 block size filesystem, 8 block size stripe.

Thanks
Fred.

[Patrick Wallek]

One thing to remember about extend based striping (-D with lvcreate) is that you can not control the stripe size. The stripe size is the same as the PE size used when the VG was created. If you have a PE size of 4MB (the default) the you will have a 4MB stripe. The only way to change the PE size is to recreate the VG.

[Dave Wherry]

Also remember that mirroring creates twice the number of writes. The first to the primary and the second to the mirror. The host waits on those to complete. In a write intensive environment it could slow you down.
The basic reason for striping is performance. Mirror for data redundancy/protection. Depending on your environment you will get different levels of performance. The types of disks you are using also makes a large difference.