Hello All,

Probably, following question may have already been discussed but i am not able to find a hit in this forum.

For a RAID array of 3+p drive and stripe size of 64K, what is a good starting point for extent and prefetch size for a tablespace defined on six logical database partitions with one cotainer on each database partition. Each database partition is on it own array group in SAN.

According to a redbook, "a good starting point would be to set extent size equal to 1 complete stripe of disks in the LUN and for the prefetch size, it must be a multiple of the extent size times the number of arrays underlying your table space.

Based on the above redbook recommendation, i came up with the

Extent sz=#disk drives in a RAID array excluding parity*RAID stripe size

extent size = 3 * 64K = 192K (or) 6 pages (where page size=32K)

Prefetch size = n * extent size * number of arrays underlying the tablespace

Prefetch size = 1 * 192 K * 6 = 1152 K (or) 36 pages

Am i right ? Please reply with your response.
for a LUN striped
across a 6+P array, set it to 6*32 K = 196 K.

As far as I understand, extent size should be strip size and prefetch size should be the number of containers * stripe size.

Thanks for your input on the extent & prefetch size.
I'm referring to a redbook"Partitioning for Performance in an e-Business Intelligence World" , page 61

Thanks

There's a white paper written in conjunction with EMC - look on DMDD that kind of explains it in detail - however that may be specific to EMC.

HI,

Are you referring to "Best Practices for EMC Symmetrix 8000 with IBM DB2 Universal Database ".

I will go thru it and get back to you soon.

Thanks