HP VMA SAN Gateway for VMA-series Memory Arrays Release Notes - May 2012 - Software OE version G5.1.0

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I/Os are NON-4KB aligned and < 256KB 512 / number of servers*
I/Os are NON-4KB aligned and > 256KB 256 / number of servers*
* where servers can be a whole physical server or a partition.
Linux
The Linux distros RHEL 5.7 and OL 5.7 have been validated on the DL980 G7 server with the HP
VMA SAN Gateway software OE version G5.1.0 and connected VMA-series Memory Arrays using
firmware version A5.1.3. Additional limitations and considerations for Linux environments are shared
in the following subsections.
Recommended Multipath Settings
For Linux environments, it is recommended to change from the default settings for multipathing. For
heavily loaded I/O environments, such as with the VMA SAN Gateway, it has proven to be more
efficient to use the ‘tur’ checker method instead of the ‘readsector0’ or ‘directio’ alternatives to check
the health of lunpaths. An example multipath setting would be:
devices {
device {
vendor "VIOLIN "
product "SAN ARRAY "
path_grouping_policy multibus
path_checker tur
getuid_callout "/sbin/scsi_id -g -u -s /block/%n"
path_selector "round-robin 0"
failback immediate
rr_weight uniform
rr_min_io 20
}
}
The ‘rr_min_io’ value denotes the minimum number of I/O operations to send down the current
lunpath before selecting the next lunpath. A lower value than typically used with standard rotational
media storage array controllers has proven better to keep all lunpaths busy. This value could be
further tuned for your specific environment based on workload and number of lunpaths.
Queue-Depth Settings for RHEL 5.7 and OL 5.7
The HBA drivers used with Linux have default LUN level queue depth values of 30 or 32 depending
upon the HBA vendor. In many cases this default value will provide good results. However in cases
where a large number of LUNs are used with a large number of server FC initiator ports, the resulting
I/O load could cause Queue-Full conditions and I/O retries leading to non-optimal performance.
For optimal I/O performance use, the following equation to determine the LUN queue depth settings
for the FC HBA driver:
LUN Queue Depth value =
(( <# gateway FC target ports> * 1024) / <# of server FC initiator ports> / <# of LUNs>)
If the resulting LUN Queue Depth value is greater than the HBA driver default (usually 30 or 32), then
use driver default setting.