HP StorageWorks 12000 - Virtual Library System EVA Gateway User Manual page 256

Because the VLS dynamically allocates storage space as user data is written, the
VLS allows you to allocate more storage for virtual media than is physically
available.
port mapping A mechanism of assigning a LUN (virtual device), such as a virtual library or
tape drive, to a specific FC host port. Port mapping allows you to load-balance
the LUNs among the FC host ports to maximize bandwidth.
At this time, you must manually load-balance the virtual tape drives in a VLS.
primary node A computer (node) that provides primary administrating and control for backup
and restore operations on a server cluster and provides communication and
control for all secondary servers on the system.
RAID A RAID volume consists of more than one drive, but appears to the operating
system to be a single logical disk. RAID improves performance by disk striping,
which involves partitioning each drive's storage space into units. By placing data
on multiple disks, I/O operations can overlap in a balanced way, improving
performance.
RAID 1-level data Consists of at least two drives that use mirroring (100% duplication of the storage
storage of data). There is no disk striping. Read performance is improved since either
disk can be read at the same time. Write performance is the same as for single
disk storage.
RAID 5-level data Provides data disk striping at the byte level and also disk stripe error correction
storage information. RAID 5 configurations can tolerate one drive failure. Even with a
failed drive, the data in a RAID 5 volume can still be accessed normally.
RAID 6-level data Provides data disk striping at the byte level and also disk stripe error correction
storage information. RAID 6 configurations can tolerate two drive failures. Even with two
failed drives, the data in a RAID 6 volume can still be accessed normally. RAID
6 read performance is similar to RAID 5, since all drives can service read
operations, but the write performance is lower than that of RAID 5 because the
parity data must be updated on multiple drives.
redundancy In a redundant system, if you lose part of the system, it can continue to operate.
For example, if you have two power supplies with one that takes over if the other
one dies, that's redundancy.
replication Similar to automigration. Data is written to virtual tape, and after the backups
are complete, the data is written to another virtual tape, known as the replication
target, over the LAN/WAN.
secondary node A computer (node) that provides secondary administrating and control for backup
and restore operations on a server cluster, and provides additional storage and
multi-pathing capabilities on the system.
secure sockets A protocol designed to enable applications to transmit information back and
layer (SSL) forth securely. Applications that use this protocol inherently know how to give
certificate and receive encryption keys with other applications, as well as how to encrypt
and decrypt data sent between the two.
Some applications that are configured to run SSL include web browsers like
Internet Explorer and Netscape, mail programs like GroupWise, Outlook, and
Outlook Express, FTP (file transfer protocol) programs, etc. These programs are
automatically able to receive SSL connections.
256 Glossary