Cisco NSS2000 - Gigabit Storage System Chassis Administration Manual page 175

Glossary of Storage-Related Terms & Acronyms
Cisco Small Business NSS2000 Series Administration Guide
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MDFS (Microsoft Distributed Filesystem): see DFS.
Mirroring: For NAS devices, the automated process of simultaneously writing data
to two (or more) hard disk drives. Mirroring creates a redundant repository of data,
such that if one of the hard disk drives (HDD) fails, the redundant drive continues to
provide access to the stored data for connected users. Network administrators
can then replace the failed drive with a new drive that can be re-mirrored to the
good drive. RAID level 1 uses mirroring.
MTBF (Mean Time Between Failures): A measurement of hardware product
reliability typically indicated in thousands, tens of thousands, or hundreds of
thousands of operational hours between failures. It is most often defined as the
average time between failures. MTBF can be derived from extensive and time
intensive testing of the working product, calculated from actual product field
performance (depending on the product, its market, its usage, and the ability to
retrieve accurate usage data), or from a calculated prediction based on known
factors. Manufacturers provide MTBF as a reference of the product's, or its
subcomponent's reliability. Customers can use the MTBF to determine their
service needs to maintain or replace the product.
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