Mylex eXtremeRAID Installation Guide download pdf (Page 61)

Glossary

775013 G-3

Hot Replacement of Disks (Hot Swap)

The design of the DAC1164 controllers allows for the replacement of failed

hard disk drives without interruption of system service. In the event of a

SCSI drive failure on a properly configured system (where the data

redundancy features of the controller are used), system service continues

without interruption. A message is generated by the system to alert the

system operator.

When a replacement drive becomes available, the system operator can

remove the failed disk drive, install a new disk drive, and instruct the

controller to “rebuild” the data on the new drive, all without interrupting

system operations.

Once the rebuild is complete, the controller will be brought back into a fault

tolerant state.

Logical Drive States

The state of a logical (system) drive can be either ONLINE, CRITICAL, or

OFFLINE. Notice that the same term “online” is used for both physical and

logical drives.

Online: A Logical Drive is in an “online” state if...

All of its participating SCSI drives are “online.”

Critical: A Logical Drive is in a “critical” state if...

It has been configured at RAID level 1, 3, 5, or 0+1; and

One (and only one) of its SCSI drives is not “online.”

A logical drive is considered “critical” because any failure of another of its

SCSI drives may result in a loss of data.

☛

Note

I/O operation can only be performed with system

drives that are online or critical.

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Mylex eXtremeRAID Installation Guide Page 61