System and performance expectations
To help determine the best way to configure your storage, rank the following three storage
characteristics in order of importance:
•
Fault tolerance (high availability)
•
I/O performance
•
Storage efficiency
With your priorities established, you can determine which striping method and RAID level to use.
As highlighted in the following section, some configuration methods offer greater fault tolerance,
while other configuration methods offer better I/O performance or storage efficiency.
RAID levels
Vraid is the HP term for the implementation of RAID (Redundant Array of Independent Disks) storage.
Vraid is also referred to as redundancy in HP management software. Virtual disks with HP Vraid
use three key RAID methods: data striping, data mirroring, and parity error checking. Unlike
traditional RAID, all HP Vraid levels distribute data across all available physical disks.
Data striping improves speed by performing virtual disk I/O with an entire group of physical disks
at the same time. Mirroring provides data redundancy by storing data and a copy of the data.
Parity also provides data redundancy by storing data and the calculated parity for each stripe of
data. If a subset of the data on a physical disk becomes corrupt or the entire physical disk fails,
the data can be automatically recovered from redundancy so that data loss does not occur.
The EVA has four Vraid types: Vraid0, Vraid1, Vraid5, and Vraid6. Each Vraid type provides
unique I/O speed and has a different level of data redundancy, which directly effects the amount
of physical space used. Once a virtual disk is created, the Vraid type or level cannot be changed.
See
Table 1 (page 6)
for a comparison of the different RAID levels.
Table 1 Raid Level Comparison
RAID method
Data redundancy
Best practices
Summary
Striping
None
IMPORTANT
: HP does not
recommend using Vraid0 for virtual
Vraid0 is optimized for I/O
speed and efficient use of
Vraid0
disks when high availability is
physical disk capacity, but
provides no data redundancy. required. Consider Vraid0 only for
noncritical storage. Vraid0 virtual
disks provide the best performance
for applications that use random I/O.
Striping and
mirroring
High
In general, Vraid1 virtual disks
provide better performance
Vraid1 is optimized for data
redundancy and I/O speed,
Vraid1
characteristics over a wider range of
application workloads than Vraid5.
but uses the most physical disk
space.
IMPORTANT
: Vraid1 uses
about 100% more physical
disk space than Vraid0.
Striping and
parity
Medium
Vraid5 virtual disks provide as good
or better performance than Vraid1
Vraid5 provides a balance of
data redundancy, I/O speed,
Vraid5
for applications that use sequential
and efficient use of physical
writes. Vraid5 has much lower
disk space. Vraid5 uses about
random write performance in
20% more physical disk space
than Vraid0.
comparison to Vraid1, but has much
higher capacity efficiency.
Striping and
double parity
Very high
Performance characteristics of Vraid6
for random and sequential write
Vraid6 is similar to Vraid5, but
provides a higher level of
Vraid6
workloads will be slightly slower than
redundancy by storing two
Vraid5. Vraid6 provides the highest
parity blocks per stripe instead
6
Review and confirm your plans
