DataDirect Networks S2A9550, Руководство пользователя

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M a n a g i n g t h e S 2 A 9 5 5 0
D a t a D i r e c t N e t w o r k s S 2 A 9 5 5 0 U s e r G u i d e
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3.3.1.4 Prefetch Settings
When the system receives a request, it can read more data than it has been requested. Prefetch tells
the system how much data to look ahead. This will improve performance if your system needs to
perform sequential reads. For random I/O applications, however, use the smallest prefetch value.
Use the CACHE PREFETCH=x command to set the prefetch that will occur on read commands for
the specified LUN. Valid range is 0 to 65535. Default setting is 1.
If the MF (Multiplication Factor) parameter is OFF, the system will only prefetch the number of
blocks specified by
PREFETCH
after every read command. If the MF parameter is ON, then the
system will multiply the transfer length of the command by the prefetch value to determine how
much data will be prefetched. A prefetch value of less than 8 is recommended when the MF
parameter is ON.
Use the CACHE MF=ON|OFF command to enable/disable the Multiplication Factor bit on the
specified LUN. Default is ON.
The Maximum Prefetch Ceiling parameter sets the maximum prefetch ceiling in blocks for
prefetches on read commands. It sets an upper limit on prefetching when the MF parameter is ON.
The system will automatically limit the amount of prefetching if the system is running low on
resources.
Use CACHE MAX=x command to set the maximum prefetch ceiling in blocks for prefetches on read
commands for the specified LUN. Valid range is 0 to 65535. Default setting is 65535.
3.3.1.5 Cache Settings Reset
The CACHE DEFAULTS command will load the default settings for all of the cache parameters for
the specified LUN’s.
3.3.1.6 Disk Configuration Settings
The writeback cache and disk timeout settings can be configured for the system. Use the DISK
command to display the current disk configuration settings
(Figure 3-30)
.
Use the
DISK TIMEOUT=x
command to set the disk timeout for an I/O request in seconds. Valid range
is 1 to 512 seconds. Default setting is 21 seconds.
Use the
DISK WRITECACHE=ON|OFF
command to enable/disable writeback caching on the disks.
Writeback caching allows the disks to increase the performance of write I/O requests by storing the
data in cache and saving the data at a later time. Default is ON.
Disk Channel Status
Figure 3-30 Disk Configuration Setting Screen
S2A [1]: disk
Disk Channel A healthy.
Disk Channel B healthy.
Disk Channel C healthy.
Disk Channel D healthy.
Disk Channel E healthy.
Disk Channel F healthy.
Disk Channel G healthy.
Disk Channel H healthy.
Disk Channel P healthy.
Disk Channel S healthy.
Disk write caching is Enabled.
Disk command timeout: 10 seconds.
Disk commands outstanding: 0
All disks are healthy.
Audio/visual settings Disabled.
Disk command AV timeout: 1
Fast AV reads: Enabled
Ordered Tag Count: 0