Scsi Tape Acceleration - Cisco MDS 9000 series Configuration Manual

SCSI Tape Acceleration

S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
Figure A-1
RTT1
RT2
RTT1
SCSI Tape Acceleration
Tapes are storage devices that store and retrieve user data sequentially. Cisco MDS NX-OS provides both
tape write and read acceleration.
Applications that access tape drives normally have only one SCSI WRITE or READ operation
outstanding to it. This single command process limits the benefit of the tape acceleration feature when
using an FCIP or FC tunnel over a long-distance WAN link. It impacts backup, restore, and restore
performance because each SCSI WRITE or READ operation does not complete until the host receives a
good status response from the tape drive. The SCSI tape acceleration feature helps solve this problem.
It improves tape backup, archive, and restore operations by allowing faster data streaming between the
host and tape drive over the WAN link.
In an example of tape acceleration for write operations, the backup server in
operations to a drive in the tape library. Acting as a proxy for the remote tape drives, the local Cisco
MDS switch proxies a transfer ready to signal the host to start sending data. After receiving all the data,
the local Cisco MDS switch proxies the successful completion of the SCSI WRITE operation. This
Cisco MDS 9000 Family I/O Accelerator Configuration Guide
A-2
SCSI Write Acceleration
Initiator MDS 9000
Initiator MDS 9000
Transfer ready
Appendix A
MDS 9000
FCIP over
WAN
Command
Transfer ready
Data transfer
Status
MDS 9000
FCIP over
WAN
Command
Data transfer
Status
SCSI Write Acceleration and Tape Acceleration
Target
FC FC
Without
acceleration
Target
FC FC
Transfer ready
With
acceleration
Figure A-2 issues write
OL-20708-01, Cisco MDS NX-OS Release 5.0(1a)