AIX Tip of the Week

Non-Strict Disk Mirroring

Audience: System Administrators

Date: July 22, 2002

The "non-strick" AIX mirroring option can be used to mirror data over fewer disks compared to the traditional "strict" mirroring option. The attached diagram illustrates both options. In both cases, the data is protected from hardware failure as no two mirror copies reside on the same physical disk.

Non-Strict Mirror

In this example, the non-strict option uses half the disk drives of the strict option. However, this can be customized this using the "mklv" command:

mklv -y strict_lv -e x -c 2 datavg 3 hdisk2 hdisk3 hdisk4

The view the physical partition layout:

lslv -m strict_lv

LP PP1 PV1 PP2 PV2 0001 0017 hdisk2 0250 hdisk3 0002 0249 hdisk3 0104 hdisk4 0003 0103 hdisk4 0018 hdisk2

To replace a failed disk, use the "migratepv" command. Here are the steps to recover from a failed disk.

  1. Backup the data
  2. Pull the failed disk, let's call it hdisk4
  3. Put in a new disk
  4. Run: cfgmgr -l <disk adapter> and the new disk will show up, let's call it hdisk5
  5. Run: extendvg <vgname> hdisk5
  6. Run: migratepv hdisk4 hdisk5
  7. Run: reducevg <vgname> hdisk4
  8. Run: rmdev -dl hdisk4

PS Thanks Dan Braden for this tip.

Bruce Spencer,