Data Availability; Raid Support; Stripe Size Migration - HP 273914-B21 - Smart Array 6404/256 RAID Controller Technology Brief

Data availability

Smart Array controllers support online array expansion, logical drive extension, stripe size migration,
and RAID migration. These technologies protect data and allow network administrators to modify the
array without interrupting user access. Smart Array controllers can monitor I/O activity, track key
parameters, predict potential problems, take corrective actions, provide automatic recovery, and
deliver full fault management to protect against downtime.

RAID support

In 1989, HP (then Compaq) was the first company to introduce RAID subsystems in the network server
marketplace. Today, RAID is an industry-standard technology and most online network data storage is
protected with some level of RAID.
Smart Array controllers support RAID levels 0, 1, 1+0, 5, 6, 50, and 60. Today, only Smart Array
controllers offer RAID 6, which provides higher fault tolerance than RAID 5 with lower implementation
costs than RAID 1+0 and greater usable capacity per unit density than RAID 1.

Stripe size migration

Using the ACU, administrators can change the stripe size of a logical drive without any downtime.
Stripe size migration can improve logical drive in response to changes in the read/write environment.
Each RAID level has a default value designed to provide good performance across many types of
applications. Table 3 shows the default values and the range of stripe sizes available for each RAID
level. Table 3 provides a generic overview of stripe sizes for the listed RAID levels and is generally
applicable to the present generation of Smart Array controllers. These values can change for certain
controllers and storage device implementations. Users should consult configuration documentation for
the specific controller and storage device in question.
Table 3. Stripe sizes available per RAID level
Fault-tolerance level
RAID 0
RAID 1 or 1+0
RAID 5
RAID 6 *
RAID 50
RAID 60 *
* Requires a valid SAAP license key
Certain applications, especially those performing mostly one type of transaction, write transactions for
example, may require adjusting stripe size to achieve optimal performance. Table 4 lists
recommended stripe sizes for general types of server applications. Administrators can start with these
general recommendations and then fine tune to determine the best overall performance for a
particular application. The ACU allows administrators to make these changes online without
disruption or data loss.
Default in KB
128
128
64
16
128
16
Available stripe sizes (KB)
8, 16, 32, 64, 128, 256
8, 16, 32, 64, 128, 256
8, 16, 32, 64, 128, 256
8, 16, 32, 64, 128, 256
8, 16, 32, 64, 128, 256, 512
8, 16, 32, 64, 128, 256
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