V
Variable prefetch
A cache prefetch strategy. The size of the data to be prefetched is the
multiple for prefetching multiplied by the length of a read command.
This strategy applies to the applications that require reading data of
variable size in a certain order or to the situations where multiple
subscribers read data concurrently but no fixed prefetch size can be set,
because the amount of pre-read data cannot be judged. An example is
the streaming media demanded by multiple subscribers who use
different bit rates.
W
Waiting
The status of hyper copy. Because the number of hyper copy that is
processed simultaneously reaches the maximum that the system
supports, the current hyper copy must wait in line.
Working
controller
The controller used by the array LUN to read and write a disk.
Write hole
A potential data corruption problem for parity RAID technology
resulting from any array failure while application I/O is outstanding,
followed by an unrelated member disk failure (some time after the array
has been returned to service). Data corruption can occur if member data
and parity become inconsistent due to the array failure, resulting in a
false regenerating when data failed member disk is subsequently
requested by an application.
Write-back cache
A cache technology. When the write operation is completed, the data
continues to be stored in the cache and therefore, the operation of writing
the data to disks will be delayed. No need to access disks during each
write operation.
Write-back cache
mirroring
A cache technology. Data is written to the local cache and at the same
time written to the opposite cache.
Write-through
cache
A cache technology. Data is written to disks. And only when the data
is safely written to disks, the procedure of write requests can be ended.
Disks need to be accessed during each write operation.
Z
Zone
In the fiber channel, a collection of the N_Port or the NL_Port which
can communicate with each other in the optical network. Only the
N_Port or the NL_Port in the same partition can communicate with each
other through the optical network.
OceanStor S5600 Storage System
Initial Configuration Guide
B Glossary
Issue 02 (2009-09-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
B-13
