Overland Storage SnapServer Administrator's Manual page 276

SnapServer GuardianOS 7.2 Administrator's Guide
disks in the pool. If a single disk fails, each block of data stored on that disk can be
reconstructed using the corresponding data block from all the other disks along with the
parity block. This means that if a single disk fails, data can still be read, albeit at a rather
slower rate (because it needs to be reconstructed, rather than read directly). For this reason,
a RAID 5 pool with a disk failure is referred to as a degraded pool.
RAID 6 (Striping with Dual Parity)
RAID 6 is similar to RAID 5 but instead of storing a single disk's worth of parity data, two
disk's worth are stored, making the pool capable of withstanding the failure of two disks.
However, there is an additional write overhead involved in calculating the double parity
data. Since RAID 6 works best with dedicated hardware, RAID 6 is only offered on systems
with a hardware RAID controller. Read performance is similar to that of RAID 0 or 5. Since
two disks are used for storing parity data, the capacity of a RAID 6 pool made up of 8 x 500
GB disks will be 3 TB.
RAID 10 (Striped Mirroring)
RAID 10 is defined as mirrored stripe sets or also known as RAID 0+1. You can build RAID
10 either directly through the RAID controller (depending on the controller) or by combining
software mirroring and controller striping, or vice versa (called RAID 01).
RAID 50
A RAID 50 combines the straight block-level striping of RAID 0 with the distributed single
parity of RAID 5. That is, a RAID 0 array striped across RAID 5 elements. It requires at least
6 disks. This can increase the performance by allowing the controller to more efficiently
cluster commands together. Fault tolerance is also increased, as one drive can fail in each
individual array.
RAID 60
A RAID 60 combines the straight block-level striping of RAID 0 with the distributed double
parity of RAID 6. That is, a RAID 0 array striped across RAID 6 elements. It requires at least
8 disks. This can increase the performance by allowing the controller to more efficiently
cluster commands together. Fault tolerance is also increased, as two drives can fail in each
individual array.
Recurring Snapshot
A snapshot that runs at an administrator-specified time and interval.
Restrict Anonymous
A Windows feature in which anonymous users cannot list domain user names and
enumerate share names. Microsoft has provided a mechanism in the Registry called restrict
anonymous for administrators to restrict the ability for anonymous logon users (also known
as NULL session connections) to list account names and enumerate share names.
The implementation of the restrict anonymous mechanism may prevent the SnapServer
from obtaining the list of account names it needs to authenticate Windows domain users.
Resynchronization
A RAID state that describes the process of integrating a new drive into the RAID.
RETMA
Short for Radio-Electronics-Television Manufacturers' Association. It is the common name
given for a 19-inch distribution frame rack for mounting components.
10400317-003 05/2012
©2010-12 Overland Storage, Inc.
 G-19