Sun Microsystems T3 Creating and Labeling a Logical Volume, Setting the LUN Reconstruction Rate

Note – Only one hot spare is allowed per array and it is only usable for the array in which it is configured. The hot spare must be configured as drive 9.

Drive 9 will be the hot spare in the unit. So, for example, should a drive failure occur on drive 7, drive 9 is synchronized automatically with the entire LUN to reflect the data on drive 7. Once the failed drive (7) is replaced, the controller unit will automatically copy the data from drive 9 to the new drive, and drive 9 will become a hot spare again.

Tip – Although they are not required, hot spares are always recommended for mission-critical configurations because they allow the controller unit to reconstruct the data from the RAID group and only take a performance hit while the reconstruction is taking place. If a hot spare is not used, the controller unit remains in write-through cache mode until the failed drive is replaced and reconstruction is complete (which could take an extended period of time). During this time, the array is operating in degraded mode.

If there is no hot spare, the reconstruction of the data will begin when the failed drive is replaced, provided RAID 1 or RAID 5 is used.

Creating and Labeling a Logical Volume

You must set the RAID level and the hot-spare disk when creating a logical volume. For the Solaris operating system to recognize a volume, it must be labeled with the format or fmthard command.

Caution – Removing and reconfiguring a logical volume will destroy all data previously stored there.

Setting the LUN Reconstruction Rate

Note – When a failed drive is disabled, the volume is operating without further redundancy protection, so the failed drive needs to be replaced as soon as possible.

Chapter 2 Configuring Global Parameters 19