You must follow the guidelines and procedures for your storage system to
maximize performance and to avoid potential I/O problems.
General guidelines
You must follow these
general guidelines when configuring your storage systems.
Avoid splitting arrays into multiple logical disks at the storage system level.
Where possible, create a single logical disk from the entire capacity
of the array.
Depending on the redundancy that is required, create RAID-5 arrays
using between 5 and 8 plus parity components. That is 5 + P, 6 + P,
7 + P or 8 + P.
Do not mix managed disks (MDisks) that greatly vary in performance
in the same MDisk group. The overall MDisk group performance is limited
by the slowest MDisk. Because some disk controllers can sustain much
higher I/O bandwidths than others, do not mix MDisks that are provided
by low-end storage systems with
those that are provided by high-end storage systems.
You must consider the following factors:
The underlying RAID type that the storage system is
using to implement the MDisk.
The number of physical disks in the RAID array and the physical
disk type. For example: 10K/15K rpm, FC/SATA.
When possible, include similarly sized MDisks in an MDisk group.
This makes it easier to balance the MDisks in the group. If the MDisks
in an MDisk group are significantly different sizes, you can balance
the proportion of space that is allocated on each MDisk by including
the larger MDisk multiple times in the MDisk list. This is specified
when you create a new VDisk. For example, if you have two 400 MB disks
and one 800 MB disk that are identified as MDisk 0, 1, and 2, you
can create the striped VDisk with the MDisk IDs of 0:1:2:2. This doubles
the number of extents on the 800 MB drive, which accommodates it being
double the size of the other MDisks.
Avoid leaving VDisks in image mode. Only use image mode to import
existing data into the cluster. To optimize the benefits of virtualization,
migrate this data across the other MDisks in the group as soon as
possible.
Follow the FlashCopy® feature
requirements before you set up the storage. Balance the spread of
the FlashCopy VDisks across
the MDisk groups and then across the storage systems.
The I/O characteristics of the application that is writing to the
source VDisk also affects the impact that FlashCopy operations have on your overall
I/O throughput.
Perform the appropriate calculations to ensure that your storage systems are
configured correctly.
If any controller that is associated with an MDisk has the allowquorum parameter
set to no, the setquorum command will fail for that
MDisk. Before setting the allowquorum parameter to yes on
any controller, check the following Web site for controller configuration
requirements.
Logical disk configuration guidelines for storage systems
Most storage systems provide
some mechanism to create multiple logical
disks
from a single array. This is useful when the storage system presents
storage directly to the hosts.
Optimal MDisk group configuration guidelines for storage systems
A managed disk (MDisk) group provides the pool of storage
from which virtual disks (VDisks) are created. You must ensure that
the entire pool of storage provides the same performance and reliability
characteristics.
FlashCopy mapping guidelines for storage systems
Ensure that you have considered the type of I/O and frequency
of update before you create the virtual disks (VDisks) that you want
to use in FlashCopy mappings.