I recently blogged about the phenomenal Oracle10g TPC-H result with HP’s Itanium2 based Superdome. I just took another look at the Full Disclosure Report to see what percentage of the gross disk capacity was used for Oracle tablespaces. When allocating space from each spindle, it is always good practice to use no more than about the outer most 60% of the platters. The sectors on the outside of each platter have higher capacity than the sectors closer to the center. I know not all storage arrays allow administrators to choose the disk geometry that derives a LUN, but if it is supported, it is good practice.
The 60% Rule Lives On
This audacious TPC-H result used 3072 36GB hard drives. Yes, folks, unfortunately for databases like Oracle more small drives are better—yet most of today’s storage arrays are shipping maximum capacity with minimum spindles. Yikes! Anyway, a storage configuration with 3072 36GB drives yields a gross capacity of 108TB. As I discussed in my first post about this TPC-H results, the ASM diskgroup consisted of 256 “disks” which were actually 138GB LUNs—an ASM diskgroup of 34.5TB. Since ASM was used with external redundancy, it is safe to presume that the LUNs were mirrored so the 108TB gross yields a RAID net of 54TB. The ASM space, therefore, consumed 63.8% of the drives’ gross capacity.
Some Things Never Change
Good fundamental principles such as preferring the outer portions of those round, brown spinning things generally stand the test of time. The storage subsystem configured for this TPC-H result prices out at nearly USD $3 million and yet the same fundamental storage allocation rules are still followed.
Audited TPC results are a wealth of information. I sure used to loathe doing them though!