Raid Availability; Raid Availability Concept; Spare Drives; Rebuilding - Intel SC5650BCDP Software User's Manual

RAID Availability

RAID Availability Concept

Data availability without downtime is essential for many types of data processing and storage
systems. Businesses want to avoid the financial costs and customer frustration associated with
failed servers. RAID helps you maintain data availability and avoid downtime for the servers
that provide that data. RAID offers several features, such as spare drives and rebuilds, that you
can use to fix any physical disk problems, while keeping the servers running and data
available. The following subsections describe these features.

Spare Drives

You can use spare drives to replace failed or defective drives in an array. A replacement drive
must be at least as large as the drive it replaces. Spare drives include hot swaps, hot spares, and
cold swaps.
A hot swap is the manual substitution of a replacement unit in a disk subsystem for a defective
one, where the substitution can be performed while the subsystem is running (performing its
normal functions). In order for the functionality to work, the backplane and enclosure must
support hot swap.
Hot-spare drives are physical drives that power up along with the RAID drives and operate in
a standby state. If a physical disk used in a RAID virtual disk fails, a hot spare automatically
takes its place and the data on the failed drive is rebuilt on the hot spare. Hot spares can be
used for RAID levels 1, IME, 5, 6, 10, 50, and 60.
Note: If a rebuild to a hot spare fails for any reason, the hot-spare drive will be marked as "failed". If the
source drive fails, both the source drive and the hot-spare drive will be marked as "failed".
Before you replace a defective physical disk in a disk subsystem, a cold swap requires that you
power down the system.

Rebuilding

If a physical disk fails in an array that is configured as a RAID 1, IME, 5, 6, 10, 50, or 60
virtual disk, you can recover the lost data by rebuilding the drive. If you have configured hot
spares, the RAID controller automatically tries to use them to rebuild failed arrays. A manual
rebuild is necessary if there are no hot spares available with enough capacity to rebuild the
failed array. Before rebuilding the failed array, you must install a drive with enough storage
into the subsystem.

Drive in Foreign State

When newly inserted drives are detected by the RAID controller, and are displayed in either
RAID BIOS Console 2 or RAID Web Console 2, their state may show as (Foreign)
Unconfigured Good, or (Foreign) Unconfigured Bad. The Foreign state indicates that the
RAID controller finds existing RAID configuration on the new drives. Since these drives
cannot be configured directly, avoid deleting data on the existing RAID by mistake. Use "Scan
for Foreign Configuration" option in RAID Web Console 2, or use "Scan Devices" option in
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Intel RAID Software User's Guide 23