AIX Tip of the Week: Configuring LVM Filesystems for Maximimum Disk Availability

Audience: Systems Administrators

Date: March 1999

The following item was found on an internal IBM web site. It describes how to configure RS/6000 disk drives for the maximum AVAILABILITY. You will note that these settings tradeoff I/O performance for availability.

1. Use 3 copies.
2. Write-verify: YES. Verify each write by performing a follow-up read.
3. INTER-policy: MINIMUM. This specifies that only as many physical volumes as there are copies should be used to
4. contain the logical volume.
5. Scheduling Policy: SEQUENTIAL. This requires the write of each copy to be performed sequentially, increasing the likeliness that at least one copy completes prior to a system failure. (Comment: this setting limits reads from only the primary mirror. In contrast, the PARALLEL option allows reads to occur from any mirror copy, which can improve read performance.)
6. Allocate each logical partition copy on a separate disk: YES. This setting will not allow any two copies of the same data to reside on the same disk.