The 8247-21L, 8247-22L, and 8247-42L systems support
the volatile adapter write cache feature with the 57D7 integrated SAS controllers or the 57B4 PCIe3
RAID SAS adapter, when configured in a single controller configuration. After the required level of
adapter firmware and Linux software operating system are
installed, this feature is enabled by default, but the feature can be disabled manually for each of
the individual RAID arrays. This feature enables a volatile write cache in the SAS RAID adapter into
which data is written. The data is then flushed to the underlying disks. This feature allows the
RAID adapter to combine multiple host write operations into fewer write operations to the disks. It
also enables the RAID adapter to issue stripe write operations to RAID 5 or 6 arrays, when a full
parity stripe of data is available in the cache.
Before you enable or disable the volatile adapter write cache, ensure that the following
requirements are met:
- The iprutils package must be at least version 2.4.10. For instruction about
obtaining this version of the iprutils package for your Linux distribution, if it is not already installed, see Updating the iprutils package.
- The SAS adapter firmware level must be at least version 14511800. For instructions about
obtaining and installing the microcode, see Updating the controller microcode.
To display and change the write cache mode, complete the following steps:
- To list the current hardware RAID arrays that are configured on the system, run the iprconfig
utility: iprconfig -c show-arrays
Information similar to the following example is
displayed:
+----------------------------------------------------------------------+
| # iprconfig -c show-arrays
| Name PCI/SCSI Location Description Status |
| -------- ------------------------- --------------------- --------------- |
| sda 0003:70:00.0/0:2:0:0 RAID 0 Array Optimized |
| sdb 0003:70:00.0/0:2:1:0 RAID 10 Array Optimized |
| sdc 0003:70:00.0/0:2:2:0 RAID 5 Array Optimized |
+--------------------------------------------------------------------------------+
- To view the current caching mode for a specific adapter, type the following command:
iprconfig -c query-write-cache-policy sda
Information similar to the following example is
displayed:
+----------------------------------------------------------------------+
| # iprconfig -c query-write-cache-policy sda |
| write back |
+--------------------------------------------------------------------------------+
- To disable the volatile adapter write cache feature for a specific adapter, type the following
command: iprconfig -c set-write-cache-policy sda writethrough
Information similar to the following example is displayed indicating the change in the caching
policy:
+----------------------------------------------------------------------+
| # iprconfig -c set-write-cache-policy sda writethrough |
| # iprconfig -c query-write-cache-policy sda |
| write through |
+--------------------------------------------------------------------------------+
