RAID Tech Talk

Stripe size: The smallest block of data read from or written to a physical drive. Modern hardware implementations let you tune this block to the typical access patterns of the applications.

Stripe width: The number of physical drives used for a stripe. As a rule, the wider the stripe, the better the performance.

Volume set: Windows NT supports the ability to concatenate space on drives to form one volume. This structure is different from a stripe because a volume set uses space sequentially. A volume set writes data to the first drive in the set until that drive is full. Then it writes data to each subsequent drive until each is full.

Write-back cache: Many modern disk controllers have several MB of cache on board. Onboard cache gives the controller greater freedom in scheduling reads and writes to disks attached to the controller. Usually, the controller lets a System Administrator determine how the cache is used. In write-back mode, the controller reports a write operation as complete as soon as the data is in the cache. This sequence improves write performance at the expense of reliability. Power failures or system crashes can result in lost data in the cache, possibly corrupting the file system.

Write-through cache: The opposite of write-back. When running in a write-through mode, the controller will not report a write as complete until it is written to the disk drives. This sequence reduces read/write performance by forcing the controller to suspend an operation while it satisfies the write request.

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