From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Anker Lerret
>> Remember that LAN-free backups are often no faster
>> than 100MB/1GB Ethernet LAN-based backups. (In a few
>> cases they will actually be slower.)
>
>Mark, can you say some more about that?  We're hoping to start doing
>LAN-free and I was hoping that we could see some nice improvements in
>large backups that go straight to tape.  Are you just talking about the
>case where the LAN is relatively uncongested and the SAN is overloaded?
>Or is there something else I'm missing?

I can't say that I've got quantifiable data; I speak from real-world
experience. SAN-based data transfer from disk to tape has been, in the
best of situations, only slightly faster than similar LAN-based data
transfer. As I said earlier, the only advantages I've ever seen to
LAN-free backups have been 
1. where the LAN is too congested (or poorly configured) to guantee
reasonable backup speeds
2. the disk storage pool is too small to handle large file backups.
3. you want to guarantee that an entire node's backups go directly to
tape

--
Mark Stapleton (mark.s AT evolvingsol DOT com)
Senior TSM engineer