RAID5 Frequently Asked Questions

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Various Questions

RAID 5 Availability

What is RAID5 availability?

RAID 5 availability is a capability to provide uninterrupted data access in case of a disk failure. Let's consider two situations:

  • you use a single disk + backup and the disk fails;
  • you use a RAID 5 and one of the member disks fails.

In the first case a backup stores data but it is impossible to get the data immediately. At first you need to restore a data copy from the backup. With a RAID 5 you can access data continuously, albeit slow.

What is hotswap?

In case of a disk failure some systems (for example PCs which use a software RAID) require a shutdown to replace a failed disk. Therefore, all the work stops, which may be undesirable. Hotswap is an ability of system to provide a disk replacement without power-off and shutdown.

What is hot spare?

Hot spare is an empty disk connected to a RAID controller in advance to replace a failed disk. When a failure of one of the disks is detected, a controller starts creating copy of lost data on a hot spare drive immediately.

What is shared hot spare?

If there are several RAID 5 arrays, then one hot spare disk may be used for all arrays. Usually it is enough to have just one disk because it is unlikely that a hot spare disk will be needed for several arrays simultaneously.

See also

Useful links

RAID Recovery Guide

RAID0 Recovery

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