About The Vds And Vss Hardware Providers; About Raid Levels - HP P2000 Reference Manual

About the VDS and VSS hardware providers

Virtual Disk Service (VDS) enables host-based applications to manage vdisks and volumes. Volume
Shadow Copy Service (VSS) enables host-based applications to manage snapshots. For more information,
see the VDS and VSS hardware provider documentation for your product.

About RAID levels

The RAID controllers enable you to set up and manage vdisks, whose storage may be spread across
multiple disks. This is accomplished through firmware resident in the RAID controller. RAID refers to vdisks
in which part of the storage capacity may be used to store redundant data. The redundant data enables
the system to reconstruct data if a disk in the vdisk fails.
Hosts see each partition of a vdisk, known as a volume, as a single disk. A volume is actually a portion of
the storage space on disks behind a RAID controller. The RAID controller firmware makes each volume
appear as one very large disk. Depending on the RAID level used for a vdisk, the disk presented to hosts
has advantages in fault-tolerance, cost, performance, or a combination of these.
NOTE: Choosing the right RAID level for your application improves performance.
The following tables:
• Provide examples of appropriate RAID levels for different applications
• Compare the features of different RAID levels
• Describe the expansion capability for different RAID levels
Table 4 Example applications and RAID levels
Application
Testing multiple operating systems or software development (where redundancy is not an issue)
Fast temporary storage or scratch disks for graphics, page layout, and image rendering
Workgroup servers
Video editing and production
Network operating system, databases, high availability applications, workgroup servers
Very large databases, web server, video on demand
Mission-critical environments that demand high availability and use large sequential workloads
Table 5 RAID level comparison
RAID Min.
level disks
NRAID 1
0 2
1 2
3 3
30 Getting started
Description
Non-RAID, nonstriped
mapping to a single disk
Data striping without
redundancy
Disk mirroring
Block-level data striping
with dedicated parity
disk
Strengths
Ability to use a single disk to store
additional data
Highest performance
Very high performance and data
protection; minimal penalty on
write performance; protects
against single disk failure
Excellent performance for large,
sequential data requests (fast
read); protects against single disk
failure
RAID level
NRAID
0
1 or 10
3
5
50
6
Weaknesses
Not protected, lower performance
(not striped)
No data protection: if one disk
fails all data is lost
High redundancy cost overhead:
because all data is duplicated,
twice the storage capacity is
required
Not well-suited for
transaction-oriented network
applications: single parity disk
does not support multiple,
concurrent write requests