Digital Equipment HSZ40, Справочное руководство

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Glossary G-11
HSZ40 Array Controller CLI Reference Manual
VCS
VAXcluster console system.
virtual terminal
A software path from an operator terminal on the host to the controller's CLI. The path can
be established via the host port on the controller (using DUP) or via the maintenance port
through on intermediary host (VCS). A virtual terminal is also sometimes called a host
console.
warm swap
A method for adding or replacing a device whereby the system remains online, but all
activity on the device’s bus must be halted for the duration of the swap.
write-back caching
A caching strategy that writes data to the cache memory, then flushes the data to the
intended device at some future time. From the user’s perspective, the write operation is
complete when the data is stored in the cache memory. This strategy avoids unnecessary
access of the devices.
write hole
Undetectable RAID level 1 or 5 data corruption. A write hole is caused by the successful
writing of some, but not all, of the storageset members. Write holes occur under conditions
such as power outages, where the writing of multiple members can be abruptly interrupted.
A battery backed-up cache design eliminates the write hole, because data is preserved and
writes can be retried.
write-through cache
A cache write strategy in which the destination of the write data is the primary storage
media. This operation may update, invalidate, or delete data from the cache memory
accordingly, to ensure that the cache does not contain obsolete data. The user sees the
operation as complete only after the backup storage device has been updated.