IBM Power System POWER7 Series, Руководство по оптимизации и настройке

Страница: 216 / 224

200
POWER7 and Optimization and Tuning Guide
– Host bus adapters (HBAs): Use enough HBAs from storage to the host server to
provide the required application bandwidth.
• Consider high-performance storage channels, such as Fibre Channel (FC)
technology instead of slower mediums.
• If possible, use dynamic multipathing to spread the I/O load across
multiple adapters.
– Redundant Array of Independent Disks (RAID): Implement storage system RAID
striping across multiple physical disks.
• Use RAID10 or RAID5, depending on the level of redundancy and total capacity
instead of the usable capacity that is needed for each file system type.
• Use Logical Volume Manager (LVM) striping instead of concatenation.
– LVM striping: When you choose the disk stripe or segment size, or array stripe size,
AIX file systems are aligned on a 16 KB boundary.
• A strip is the size of data to be written to each physical disk in the array. A stripe is
the size of the full write across all the physical disks in the array. For example: strip
size x number of disks = stripe size.
• The AIX LVM stripe size that you can select from the
smit lv create
panel is the
single strip size (not stripe). It is the size of data to be written to each of the array
disks; it is not the full stripe size across all the physical disks. Consider using an
LVM stripe size of 64 KB or 128 KB. Stripe sizes of 256 KB or 512 KB show better
I/O performance in the case of SAS 9 workloads.
• Synchronize SAS BUFSIZE with the storage-system stripe size and the AIX LVM
stripe size (if you are using LVM striping) and VMM read-ahead increments.
• Synchronizing I/O sizes streamlines I/O processing and reduces the number of I/O
requests to the storage subsystem.
Disk storage tuning
From a high level, the AIX I/O stack contains several layers that an I/O must traverse. At each
layer, AIX tracks the I/O. Some of the layers have specific queues that are useful to consider
tuning. The I/O stack layers are:
򐂰 Application
򐂰 File system (optional)
򐂰 LVM (optional)
򐂰 Subsystem device driver (SDD) or SDD Path Control Module (SDDPCM) (if used)
򐂰 hdisk device driver
򐂰 Adapter device driver
򐂰 Interconnect to the disk
򐂰 Disk subsystem
򐂰 Disk