stripe size for metalun

See the MetaLUN Best Practice guide - see page 19 for an explanation of metaLUN stripe size.

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/H1024.1_clariion_metaluns_cncpt_wp_ldv.pdf

glen

Hi Glen,

I read the document, however, I need to validate the stripe size of the first component. I did not see how to do that in the document. If I missed it, I am sorry.

Admingirl

Just to clarify, these luns were already setup by someone else no longer here and I need to validate that.

By default all LUNs created will have the Stripe Element size set to 128 blocks (64KB). If you have a 4+1 Raid 5, then you multiple the number of data disks times the Stripe Element to get the LUN stripe size. For a 4+1, the stripe size is 4 (data disks) * 64KB = 256KB.  If you have a 6+1 R5, then you get 6 * 64KB = 384KB Stripe size. Once a LUN is actually in a metaLUN, you can not see the Element Size. When you look at the Properites of a non-metaLUN LUN, the value you look for is called Element Size - the normal setting is 128 - this is the number of blocks - divide by 2 and you get the size - 128 / 2 = 64KB.

glen

A MetaLUN Component lun is the same as a standard LUN. So you need to find the RAID type and number of disks for the RAID Group that the first component is bound to. Stripe size is 64KB * number of data disks as mentioned in a previous response. So if the RAID Group is a 5 disk RAID5 group (aka RAID5 4+1) then stripe size is 64KB * 4 = 256KB.

be careful with the 128K/2 calculation, this only works because we're using 512bytes per sector, which happens to go 2 times into 1024 (used to represent 1K).

If the bytes per sector are, for example, 520bytes then your 128/2 will not be correct.

In clariion sector contains 512 byte of data and 8 byte of metadata totalling 520 bytes..So it sounds like a clarification needed now :)

Ignore the extra 8 bytes - it's hidden and will not affect the calculation

glen