iSCSI Protocol Architecture
iSCSI Applications
Remote Backup Applications
iSCSI Backup Server
FC-iSCSI
FC Hosts
Gateway
LAN
WAN FC SAN
iSCSI Storage FC Tape
Library FC Storage
• iSCSI can directly address remote (FC or iSCSI)
block storage devices across a WAN
• Bandwidth and especially latency are key
concerns
Remote backup may become a key application for iSCSI. iSCSI can be used
to enable “remote tape vaulting” solutions in which backups are located at a
distance from the primary data centre. iSCSI allows customers to move
backups off-site for disaster protection.
Remote backup solutions are complex solutions that require careful planning
and performance tuning. Tape drives are streaming media devices—data is
read and written sequentially at a constant speed. If the storage network
cannot supply data as fast as the tape drive writes data, or if the data stream
is interrupted, the tape drive must stop, rewind to the last written byte, and
restart. High latency may be tolerable if it is consistent, but varying latency can
be a problem. If bandwidth is too low or latency varies too high, backup
performance will be severely degraded due to the constant tape drive reset
operations. Proper IP network design is crucial for remote tape backup
operations.