Sun T4 Storage Arrray and BAARF

SLAC has used Sun Storage devices for many a year. Due to flexibility requirements databases associated with experiments are provided with their own server. Due to space requirements, I've always divided a Storedge array thus: Two disks, total as a RAID 10, the rest of the disks save one as a RAID 5 stripe, and the last disk as a hot spare. Online redologs go on the mirrored portion, and the data, rollback, temporary, and other segments are placed on the RAID 5 stripe. A group of online redologs is also "duplexed" off the array to internal disk. Archived logs are also written to another internal disk.

This has worked fairly well. The main excepetion being large hash joins. With a T4 array and its 14 ~140 GB disk, I can possilbly use RAID 10 for both the online redo logs and the various segments. I'm not sure if that will result in better performance. There is advice to use RAID 5 if 90% or more of the operations are reads and 10 if not. I don't know the distribution of reads and writes.

RAID 5 has worked well for us. The one notable exception is large hash joins which may do a large number of direct writes to temporary segments.

What are others with T4's doing?

Ian MacGregor
Stanford Linear Accelerator Center

Ian MacGregor
Stanford Linear Accelerator Center
ian_at_slac.stanford.edu

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