Grass Valley Network Attached Storage System Serial ATA Network User Guide v.1.0.04 - Manual (Page 150)

Set RAID Controller Defaults
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Discontinuity Enabled When discontinuity is enabled, the device server
prefetches across time discontinuities, such as cylinders
or cache segment boundaries.
Read Ahead
(Prefetch) Enabled Reading ahead improves data retrieval performance
because the controller always reads a full data stripe into
cache. This increases the likelihood of finding requested
data in cache, which in turn decreases disk accesses and
improves performance. This is especially useful for
transfers that are small relative to the size of cache. If the
stripe size is 8KB and the read request is for 1KB, the
controller reads 8KB. If subsequent read requests are for
sequential data, that data already will be in cache. Time
spent reading the drive is minimized.
Static Cache
Segment
Allocation Disabled Static Cache Segment Allocation (SCSA) allows you to
reserve a number (divisible by 2) of cache segments for
write and write verify operations. SCSA is required
when WCM is enabled.
Conservative
Cache Mode Disabled When conservative cache mode is enabled, the controller
does not cache write data unless the battery is fully
charged. This provides additional data integrity. When
conservative cache mode is disabled, the controller
caches write data, no matter what the state of the battery.
Cache Segments 255 The number of cache segments depends on the size of a
cache segment and the total size of cache. It is the
number of segments into which cache memory is
divided. The minimum is 16. The maximum is 65,535.
Segments are contiguous logical blocks which divide the
total cache memory into pieces. Segments are constantly
reused as data is overwritten.
Write Segments 32 Segments are contiguous logical blocks that divide the
total cache memory into pieces. Segments are constantly
reused as data is overwritten. The number of write
segments you can have depends on the size of a write
segment and the total size of cache. The maximum size
of a write segment is 4 megabytes. (If cache memory is
128 MBs, the minimum number of write segments is 32.)
The write segment field is used if SCSA is enabled. It is
the number of segments from the cache segment pool
that are allocated exclusively for caching write
operations. This value must be divisible by two and can
range from four to the number of cache segments minus
one. The number of cache segments minus the number of
write segments is the number of cache segments
available for read operations. Enabling or disabling
WCM does not change the value of this field.
Field Default Description