Frecovery slow across network

[Alex Ng Chong Yau]

SDLT tape drive is mounted to server a and did frecovery across network to server b(RP series). both server also is using 1Gb Ethernet card and has been set it to full duplex. need some trooubleshooting guide on this. File size is about 71GB.

[Steven E. Protter]

Shalom Alex,

Thats a pretty big backup.

Things to check:
1)lanadmin -x 0 (change zero to match the numeric section of lan0 if the NIC involved is lan0. Use lanscan to get the data). What you are looking for here is full duplex GB connection.
2) Do a test file server to server via sftp and see what speeds you get.
3) Take a look for network congestion with wireshark, tcpdump or http://www.hpux.ws/system.perf.sh
4)What is the network mount? NFS, Samba, performance analysts with inquiring minds wnat to know.
5) What is the OS and is it properly patched.
6)GB networking on HP-UX requires autonegtiate, anything else produces awful results.

SEP

[Bill Hassell]

The SDLT tape is too fast for the speed of the network. Modern tape drives need dozens of megabytes per second to work correctly. A 1Gb network can only handle about 50-70Megs per second. If the tape requires more to keep it streaming, the tape must stop, reverse direction, then resync when enough data arrives and start running at full speed. This can reduce the backup performance by 10:1 to even 100:1 slower. This problem is so pervasive with high end tape drives that some manufacturers like HP have designed DRM circuitry (Data Rate Matching) to literally slow the tape down so it does not have to stop and reverse.

Even so, the minimum DRM capability is about 27Megs/second so if the network cannot run at least that fast, the same drastic reduction will still take place. You will probably need to purchase Auto Port Aggregation (APA) and setup at least two 1Gb LAN links to keep the tape running full speed.