Overland Storage SnapServer Administrator's Manual page 263

SnapServer 7.0 Administrator's Guide
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.
Rollback
A snapshot feature that allows the administrator to restore a volume to a previous state as
archived in a snapshot without resorting to tape.
Round Robin
The Round Robin path selection policy causes all healthy paths to be used for I/O. Paths are
used in a round-robin order.
Router
A router is a device that enables connectivity between Ethernet network segments.
SAN
Short for Storage Area Network. Data storage connected to a network that provides network
clients access to data using block level protocols. To the clients, the data storage devices
appear local rather than remote. An iSCSI SAN is sometimes referred to as an IP-SAN.
SAS
Short for Serial Attached SCSI. It is a point-to-point serial protocol that replaces parallel
SCSI bus technology (multidrop) and uses the standard SCSI command set. It has no
termination issues, supports up to 16,384 devices (using expanders), and eliminates clock
skew. It consists of an Initiator that originates device service requests, a Target containing
logical units that receives device service requests, and a Service Delivery Subsystem that
transmits information between the Initiator and the Target.
SCSI
Short for Small Computer System Interface. SCSI is an industry standard for connecting
peripheral devices and their controllers to an initiator. Storage devices are daisy-chained
together and connected to a host adapter. The host adapter provides a shared bus that
attached peripherals use to pass data to and from the host system. Examples of devices
attached to the adapter include disk drives, CD-ROM discs, optical disks, and tape drives.
In theory, any SCSI device can be plugged into any SCSI controller.
SCSI addressing
Each device supported by a SCSI adapter has its own unique SCSI address, which dictates
the device's priority when arbitrating for access to the SCSI bus. A SCSI address of 7 has
the highest priority. For a fast/wide SCSI adapter that supports up to 16 devices, the next
highest priority address is 6, then 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, and 8. The narrow
SCSI adapter supports up to eight devices, including itself. The SCSI address 7 has the
highest priority, followed by 6, 5, 4, 3, 2, 1, and 0.
SCSI bus
A SCSI bus provides a means of transferring data between SCSI devices. A SCSI bus is
either an 8- or 16-bit bus that supports up to 8 or 16 devices, including itself. The bus can
consist of any mix of initiators and targets, with the requirement that at least one initiator
and one target must be present.
10400317-001 10/2011
©2010-11 Overland Storage, Inc.
GL-17