56
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
M a n a g i n g t h e S 2 A 9 5 5 0
3.3.2
Audio/Visual Settings of the System
The audio and visual settings of the system and the disks can be tuned to provide better performance
and a lower latency. The writeback and prefetch settings for each LUN are changed with the
CACHE
command.
The
AV
command will display information about the audio/visual settings of the system
.
Use the
AV FASTAV=ON|OFF
command to enable/disable the disk fast audio/video read options for
streaming data. When enabled, the system will start the data transfer for read operations before all
of the disk commands have finished. This feature reduces the latency for read operations but the
system will be unable to check the integrity of the data. This parameter is saved on a LUN basis. Use
LUN=x command to change the settings for a single LUN. Default setting is OFF.
NOTE :
Note
: When FASTAV mode is enabled, the
S2A9550
no longer checks data in real-time
.
Use the
AV DISKAV=ON|OFF
command to enable/disable the disk audio/video options for streaming
data. When enabled, the disks will adjust the disk parameters to minimize the latency for data
transfers by disabling non-essential features which may impact performance. Note that changing the
disk parameters can adversely affect the I/O operation of the system. This parameter should only be
adjusted when the system is idle. Default setting is OFF.
NOTE :
Note
: When AV mode is enabled, the
S2A9550
will not retry check conditions on disks. Since
this increases the risk of disk failures, this should be used in AV environments only.
The
AV TIMELIMIT=x
command specifies what the recovery time limit is for the drives when DISKAV
is enabled. This is the maximum amount of time that a disk can use for the data error recovery in one
millisecond increments. The parameter is located in bytes 10 and 11 of the Read-Write Error
Recovery mode page on the disks. The recovery time limit of each disk will be set to its default value
when
DISKAV=OFF
. Note that changing the disk parameters can adversely affect the I/O operation
of the system. This parameter should only be adjusted when the system is idle. Valid range is 0 to
65535. Default setting is 65535.
The
AV ARRE=ON|OFF
command specifies what the Automatic Read Reallocation Enabled (ARRE)
bit will be set to on the drives when DISKAV is enabled. When enabled, the disks will be automatically
reallocate defective data blocks during read operations. When disabled, the disks will not reallocate
defective data blocks during read operations. Automatic Write Reallocate Enabled (AWRE) is always
enabled. The parameter is located in bit 6, byte 2 of the Read-write error recovery mode page on the
disks. The ARRE of each disk will be set to its default value when
DISKAV=OFF
. Note that changing
the disk parameters can adversely affect the I/O operation of the system. This parameter should only
be adjusted when the systems is idle. Default setting is OFF.
Current LUN Audio/Visual Settings
Maximum
Prefetch
LUN
Write
Caching
x 1
---------------------------------------------------------------
On
Off
0
Disk Audio/Visual settings are Disabled, Using disk defaults
Figure 3-31 Current Audio/Visual Settings
Fast AV
x 1
On
Off
1
x 1
On
Off
2
S2A [1]: av
Label
Early Error Recovery: Enabled
Automatic Read Reallocation: Disabled
Read Retry Count: 1
Write Retry Count: 1
Recovery Time Limit: 65535
Ordered Tag Count: 0
Summary of Contents for S2A9550
Page 1: ...DataDirect Networks Silicon Storage Appliance S2A9550 User Guide Rev 4 0 ...
Page 13: ...SECTION 1 Introducing the S2A9550 ...
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Page 21: ...SECTION 2 Installing the S2A9550 ...
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Page 24: ...Installation 12 DataDirect Networks S2A 9550 User Guide This page is intentionally blank ...
Page 43: ...SECTION 3 Using the S2A9550 Management Administrative Facilities ...
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Page 93: ...SECTION 4 Supporting the S2A9550 ...
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Page 113: ...SECTION 5 Appendices ...