Fcip Tape Acceleration - Cisco MDS 9000 series Configuration Manual

Configuring FCIP
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
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FCIP 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 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 FCIP 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
response allows the host to start the next SCSI WRITE operation. This proxy method results in more
data being sent over the FCIP tunnel in the same time period compared to the time taken to send data
without proxying. The proxy method improves the performance on WAN links.
Cisco MDS 9000 Family NX-OS IP Services Configuration Guide
2-28
TCP Connection Information
Write Accelerator statistics
6091 packets in
0 frames dropped 0 CRC errors
0 rejected due to table full
0 ABTS sent 0 ABTS received
0 tunnel synchronization errors
37 writes recd 37 XFER_RDY sent (host)
0 XFER_RDY rcvd (target)
37 XFER_RDY rcvd (host)
0 XFER_RDY not proxied due to flow control (host)
0 bytes queued for sending
0 estimated bytes queued on the other side for sending
0 times TCP flow ctrl(target)
0 bytes current TCP flow ctrl(target)
5994 packets out
Chapter 2 Configuring FCIP
Figure 2-14 issues write
OL-19525-01,Cisco MDS NX-OS Release 4.2(1)