Setting Parameters For Emulex Or Qlogic Adapters - IBM TotalStorage DS6000 Attachment Manual

Setting parameters for Emulex or QLogic adapters

This section provides instructions for setting parameters for Emulex or QLogic
adapters.
1. Type cd /etc to change to the /etc subdirectory.
2. Backup the system file in the subdirectory.
3. Edit the system file and set the following parameters for servers with
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DS6000 Host Systems Attachment Guide
following line to the /etc/system file to set the sd_io_time parameter for
the storage unit LUNs:set sd:sd_io_time=0x78
sd_retry_count
This parameter specifies the retry count for disk operations. Add the
following line to the /etc/system file to set the sd_retry_count parameter
for the storage unit LUNs: set sd:sd_retry_count=5
maxphys
This parameter specifies the maximum number of bytes that you can
transfer for each SCSI transaction. The default value is 126976 (124
KB). If the I/O block size that you requested exceeds the default value,
the request is broken into more than one request. You should tune the
value for the application requirements. For maximum bandwidth, set the
maxphys parameter by adding the following line to the /etc/system file:
set maxphys=1048576 (1 MB)
Note: Do not set the value for maxphys greater than 1048576 (1 MB). Doing so
can cause the system to hang.
configurations that only use Emulex or QLogic adapters.
sd_max_throttle
This sd_max_throttle parameter specifies the maximum number of
commands that the sd driver can queue to the host adapter driver. The
default value is 256, but you must set the parameter to a value less
than or equal to a maximum queue depth for each connected LUN.
Determine the value by using the following formula: 256 ÷ (LUNs per
adapter) where LUNs per adapter is the largest number of LUNs that
are assigned to a single adapter.
To set the sd_max_throttle parameter for the storage unit LUNs in this
example, add the following line to the /etc/system file: set
sd:sd_max_throttle=5
sd_io_time
This parameter specifies the time-out value for disk operations. Add the
following line to the /etc/system file to set the sd_io_time parameter for
the storage unit LUNs: set sd:sd_io_time=0x78
sd_retry_count
This parameter specifies the retry count for disk operations. Add the
following line to the /etc/system file to set the sd_retry_count parameter
for the storage unit LUNs: set sd:sd_retry_count=5
maxphys
This parameter specifies the maximum number of bytes you can
transfer for each SCSI transaction. The default value is 12 6976 (124
KB). If the I/O block size that you requested exceeds the default value,
the request is broken into more than one request. You should tune the