User manual

FIBRE-to-SAS/SATA RAID SUBSYSTEM
User Manual
55
RAID 1 – Mirroring
In a RAID 1 system, the data is stored
twice by writing it to both the data disk
(or set of data disks) and a mirror disk
(or set of disks). If a disk fails, the
controller uses either the data drive(s)
or the mirror drive(s) for data recovery
and continues operation. You need at
least 2 disks for a RAID 1 array. RAID 1
RAIDs give good fault tolerance but is
more suited to applications where
performance is not a critical factor. The
following illustration shows a typical
RAID 1.
Advantages Disadvantages Ideal Use
Excellent read speed and a
write-speed that is
comparable to that of a
single disk.
If a disk fails, data does not
have to be rebuilt, it can
simply be copied to the
replacement disk.
Very simple technology.
The main
disadvantage is that
the effective storage
capacity is only half of
the total disk capacity
because all data gets
written twice.
Ideal for
mission critical
storage, e.g.
accounting
systems.
Suitable for
small servers in
which only two
disks will be
used.
RAID 10 – A Stripe of Mirrors
A RAID 10 RAID combines both a RAID 0 and a RAID 1. Data is striped across
multiple drives and these stripes are then mirrored on identical drives. This RAID
level gives excellent read/write performance with good fault tolerant characteristics
also. You need at least 4 disks to implement a RAID 10 RAID. The following
illustration shows a typical RAID 10.
Advantages Disadvantages Ideal Use
High fault tolerance
characteristics.
Excellent performance
through use of striped
segments and load bal-
ancing across multiple
drives
Very expensive to
implement needing at
least 4 disks.
Not a very scalable
solution.
Ideal for use in gen-
eral file server appli-
cations.
Can be used in high
read/write applica-
tions such as image
processing, editing,
etc.