Matching storage stripe size with ASM allocation unit?

I heard an Oracle consultant suggest that the storage should be created with
stripe size 1M for ASM, because the default ASM allocation unit (probably
_asm_ausize) is 1M. He says most shops have much smaller stripe size. I asked
since it's too late for the storage team, what if we lower our ASM allocation
unit size? He gives no comment except he doesn't recommend.

Now I think about it. The ASM 1M allocation unit is for allocation or
deallocation. It can't be I/O chunk size, which is still from db_block_size up
to that multiplied by db_file_multiblock_read_count. The ideal stripe size may
be typical I/O size dictated by the most frequently run SQL divided by number
of disks in the striping setup (or larger than that). The ASM 1M size only
plays a role when you create, resize or drop a datafile, not normally done
anyway. Comments are welcome.

Yong Huang


      
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