About Size Representations - HP P2000 Reference Manual

Table 5 RAID level comparison (continued)
RAID Min.
level disks
5 3
6 4
10 4
(1+0)
50 6
(5+0)
Table 6 Vdisk expansion by RAID level
RAID level Expansion capability
NRAID Cannot expand.
0, 3, 5, 6 You can add 1–4 disks at a time.
1 Cannot expand.
10 You can add 2 or 4 disks at a time.
50 You can add one sub-vdisk at a time. The added sub-vdisk must contain the same
number of disks as each of the existing sub-vdisks.

About size representations

Parameters such as names of users and volumes have a maximum length in bytes. ASCII characters are 1
byte; most Latin (Western European) characters with diacritics are 2 bytes; most Asian characters are 3
bytes.
Operating systems usually show volume size in base 2. Disk drives usually show size in base 10. Memory
(RAM and ROM) size is always shown in base 2. In SMU, the base for entry and display of storage-space
sizes can be set per user or per session. When entering storage-space sizes only, either base-2 or base- 1 0
units can be specified.
Description
Block-level data striping
with distributed parity
Block-level data striping
with double distributed
parity
Stripes data across
multiple RAID- 1
sub-vdisks
Stripes data across
multiple RAID-5
sub-vdisks
Strengths
Best cost/performance for
transaction-oriented networks;
very high performance and data
protection; supports multiple
simultaneous reads and writes;
can also be optimized for large,
sequential requests; protects
against single disk failure
Best suited for large sequential
workloads; non-sequential read
and sequential read/write
performance is comparable to
RAID 5; protects against dual disk
failure
Highest performance and data
protection (protects against
multiple disk failures)
Better random read and write
performance and data protection
than RAID 5; supports more disks
than RAID 5; protects against
multiple disk failures
HP P2000 G3 MSA System SMU Reference Guide
Weaknesses
Write performance is slower than
RAID 0 or RAID 1
Higher redundancy cost than
RAID 5 because the parity
overhead is twice that of RAID 5;
not well-suited for
transaction-oriented network
applications; non-sequential write
performance is slower than RAID
5
High redundancy cost overhead:
because all data is duplicated,
twice the storage capacity is
required; requires minimum of four
disks
Lower storage capacity than RAID
5
Maximum disks
1
16
2
16
32
31