Enable Write Cache on SMW Boot RAID Volume

Cray SMW boot RAID storage has write cache disabled by default to reduce risk to data integrity. If high write rates are reducing performance and data integrity mitigations are in place, sites can use this procedure to enable write cache on selected storage volumes.

This procedure assumes the following:
  • Familiarity with Cray FN5338 "Write cache support statement"
  • The SANtricity Storage Manager has been installed.
  • The SMW boot RAID has been configured for a NetApp, Inc. storage device.
  • The user is logged on to the SMW as crayadm.

To reduce risk to end-user data integrity, all SMW boot RAID storage arrays are shipped (or configured, for a fresh install) with write cache support disabled. However, there are situations in which sites may want or need to enable write cache on one or more storage volumes to better handle high write rates. ALPS requires write caching, for example, so the volume that contains the ALPS shared file system will need to have write cache enabled.

This procedure enables write cache on a single volume of an existing NetApp, Inc. storage device. Repeat this procedure for each volume to be write-cache enabled.

To mitigate the risk to data integrity, write caching should be used only with battery backup and controller mirroring.

  1. Start the SANtricity Storage Manager. 
    crayadm@smw> /usr/bin/SMclient
  2. Select the storage array containing the volume to be write-cache enabled.
  3. Locate the volume to be write-cache enabled, right-click it, then select Change > Cache Settings.
  4. Enable the desired cache settings.