Online Spares; Logical Storage Elements; Logical Drives (Luns) - HP StoreEasy 1000 Administrator's Manual

Table 6 Summary of RAID methods
Maximum number of
hard drives
Tolerant of single hard
drive failure?
Tolerant of multiple
simultaneous hard
drive failures?

Online spares

Further protection against data loss can be achieved by assigning an online spare (or hot spare)
to any configuration except RAID 0. This hard drive contains no data and is contained within the
same storage subsystem as the other drives in the array. When a hard drive in the array fails,
the controller can then automatically rebuild information that was originally on the failed drive
onto the online spare. This quickly restores the system to full RAID level fault tolerance protection.
However, unless RAID Advanced Data Guarding (ADG) is being used, which can support two
drive failures in an array, in the unlikely event that a third drive in the array should fail while data
is being rewritten to the spare, the logical drive still fails.

Logical storage elements

Logical storage elements consist of those components that translate the physical storage elements
to file system elements. The HPE StoreEasy 1000 Storage uses the Window Disk Management
utility to manage the various types of disks presented to the file system. There are two types of
LUN presentation: basic disk and dynamic disk. Each of these types of disk has special features
that enable different types of management.

Logical drives (LUNs)

While an array is a physical grouping of hard drives, a logical drive consists of components that
translate physical storage elements into file system elements. A LUN may also be referred to as
a virtual disk.
It is important to note that a LUN may span all physical drives within a storage controller
subsystem, but cannot span multiple storage controller subsystems. The multiple storage controller
subsystems could indicate multiple controllers or external enclosures.
Figure 44 Two arrays (A1, A2) and five logical drives (L1 through L5) spread over five
physical drives
NOTE: This type of configuration may not apply to all HPE StoreEasy 1000 Storage systems
and serves only as an example.
118 Storage management overview
RAID 0 Striping RAID 1+0
(no fault Mirroring
tolerance)
N/A N/A
No Yes
No If the failed
drives are not
mirrored to
each other
RAID 5 RAID 6
Distributed (ADG)
Data Guarding
14 Storage
system
dependent
Yes Yes
No Yes (two
drives can
fail)
RAID 50 RAID 60
14 Storage
system
dependent
Yes Yes
No Yes (Two
drives can
fail)