General Guidelines

• Disk and controllers - Place drives in a metadevice on separate drive paths. For SCSI drives, this means separate host adaptors. For IPI drives, this means separate controllers. Spreading the I/O load over several controllers improves metadevice performance and availability.

  For SPARCstorage Arrays, you should use drives in a mirror on different chassis, if possible. This type of configuration ensures that all mirror data would survive a SPARCstorage Array chassis failure. If you cannot spread drives across different chassis, then use drives in different trays. This enables you to offline submirrors and the tray to be spun down or removed for maintenance while the mirror stays online.

  For example, consider a two-way mirror with each submirror composed of a concatenation of three SPARCstorage Array disks. One submirror would consist of three disks in tray 1, and the other submirror would consist of drives in tray 2. Using the command line interface to initialize this configuration would look like this:

# metainit d1 3 1 c0t0d0s2 1 c0t0d1s2 c0t0d2s2
d1: Concat/Stripe is setup
# metainit d2 3 1 c0t2d0s2 1 c0t2d1s2 c0t2d2s2
d2: Concat/Stripe is setup
# metainit d0 -m d1
d0: Mirror is setup
# metattach d0 d2
d0: Component d2 is attached

Strings t0 and t1 are contained in tray 1, t2 and t3 in tray 2, and t4 and t5 are in tray 3. Hence, in the above commands, to create submirrors in different trays, we use string t0 for one submirror, and t2 for the second submirror.

• System Files - Never edit or remove the /etc/lvm/mddb.cf or /etc/lvm/md.cf files.

  Make sure these files are backed up on a regular basis.

• After a slice is defined as a metadevice and activated, do not use it for any other purpose.

• Have a hardcopy of output from the prtvtoc(1M) command in case you need to reformat a bad disk.