Connected: An Internet Encyclopedia
4.8 Stable storage
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4.8 Stable storage
4.8 Stable storage
NFS version 3 protocol servers must be able to recover
without data loss from multiple power failures (including
cascading power failures, that is, several power failures in
quick succession), operating system failures, and hardware
failure of components other than the storage medium itself
(for example, disk, nonvolatile RAM).
Some examples of stable storage that are allowable for an NFS
server include:
- Media commit of data, that is, the modified data has
been successfully written to the disk media, for example,
the disk platter.
- An immediate reply disk drive with battery-backed
on-drive intermediate storage or uninterruptible power
system (UPS).
- Server commit of data with battery-backed intermediate
storage and recovery software.
- Cache commit with uninterruptible power system (UPS) and
recovery software.
Conversely, the following are not examples of stable
storage:
- An immediate reply disk drive without battery-backed
on-drive intermediate storage or uninterruptible power
system (UPS).
- Cache commit without both uninterruptible power system
(UPS) and recovery software.
The only exception to this (introduced in this protocol
revision) is as described under the WRITE procedure on the
handling of the stable bit, and the use of the COMMIT
procedure. It is the use of the synchronous COMMIT procedure
that provides the necessary semantic support in the NFS
version 3 protocol.
Next: 4.9 Lookups and name resolution
Connected: An Internet Encyclopedia
4.8 Stable storage