Storage Smarts Answer #38: Controller failure |
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By SearchStorage.com editors
13 Jan 2002 | SearchStorage.com |
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Storage Smarts
QUESTION OF THE WEEK:
Disk mirroring provides data protection in the case of disk failure because data is constantly updated to both disks, where each relies upon a common controller. However, there is an inherent problem in disk mirroring. What is it?
a. Drive reliability is eliminating the need for mirroring
b. Access to data is threatened if the controller fails
c. Data can't be mirrored remotely
d. Mirroring can't handle planned outages
e. Data sets can't be kept in synch
Were you correct? This week's answer is:
b. Access to data is threatened if the controller fails
Disk mirroring (also known as RAID-1) is the practice of duplicating data in separate volumes on two hard disks to make storage more fault-tolerant. Mirroring provides data protection in the case of disk failure, because data is constantly updated to both disks. However, since the separate disks rely upon a common controller, access to both copies of data is threatened if the controller fails. Disk duplexing overcomes this problem; the use of redundant controllers enables continued data access as long as one of the controllers continues to function.
For more information:
Mirroring strategies
SD2002: Mirroring still crucial despite disk drive improvements
Disk mirroring - local or remote
Talking failure in disk arrays
Ask W. Curtis Preston your backup and recovery questions.
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