HP Compaq Integrated Smart Array Controller - Manual (Page 129)

Understanding Drive Arrays B-23
Compaq Confidential – Need to Know Required
Writer: CDresden Project: Compaq Integrated Smart Array Controller User Guide Comments:
Part Number: 153236-001 File Name: i-appb Understanding Drive Arrays.doc Last Saved On: 8/27/99 11:35 AM
A RAID 5 (Distributed Data Guarding) Logical Drive
RAID 5 logical drives:
■ Can sustain a single drive failure. The logical drive will be in a
“regenerating” condition if one drive is failed.
■ Will be in a “failed” condition if more than one drive is failed.
■ Will be in a “rebuilding” condition if a previously failed drive has been
replaced and the replacement drive is rebuilding. The volume may also
be in a “rebuilding” condition following a drive failure if a spare drive
was previously assigned and is rebuilding.
Spare Drives
In case of a drive failure, if a spare drive is assigned and available, the spare
drive acts as an immediate replacement for the failed drive. Data is
automatically reconstructed from the remaining drives in the volume and
written to the spare drive via the Automatic Data Recovery process. Once the
spare drive is completely built, the logical drive is again running at full fault
tolerance, and is then able to sustain another subsequent drive failure. Note,
however, that if another drive were to fail before the spare drive is completely
built, the spare drive cannot prevent failure of the entire logical drive. Also,
note the possibility that non-correctable disk errors can prevent completion of
the Automatic Data Recovery process.
Replacing a Failed Drive
Failed drives in hot-plug trays can be removed and replaced while host system
and storage system power is in Off/Standby mode. Hot-plug drives can also be
replaced when the power is Off.
CAUTION: Never turn off an external storage system while the host system
power is on because all drive will fail and fault tolerance will likely be
compromised.
When a hot-plug drive is inserted, all disk activity on the controller will be
temporarily paused while the drive is spinning up (usually 20 seconds or so). If
the drive is inserted while power is On, in fault-tolerant configurations,
recovery of data on the replacement drive will automatically begin (indicated
by blinking online LED).