Friday, February 17, 2006

SQL Server vs SAN

Recently we have been looking at some performance problems on some of our servers. I found some interesting information concerning SAN's so here is a little high level overview of things to remember.

  • Format the Data drives with 64k sector size, the Log drive with at least 8k.
  • Align the disks using diskpar in Windows 2003 (diskpart for SP1+) or do this at SAN level if possible (10%-20% improvement in some studies).
  • Use StorPort drivers for your HBA's. SCSIPort was designed for direct attached storage while StorPort is optimized for SAN I/O) - Info
  • Choose RAID 10 over RAID5. Although certain SAN's have optimized RAID5 technology that reduce the overhead RAID10 is still the preferred level.
  • Spread over as many disks as possible.
  • Always separate your data from your log drives. Log is sequential while data is more random I/O, mixing these might cause log latency.
  • Stress test your SAN with realistic file sizes.

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