From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Mike Eggleston
>I know that TSM can do both serverfree and lanfree. My
>impression of these is that for lanfree the client node
>asks TSM over the network where to place files. The TSM
>server tells the node  and the node talks to the tape
>drives directly. 

That is essentially correct.

>Since I have four tape drives (that I can
>put onto the SAN fabric) then only four nodes can backup
>at once?

Yes; you can only have as many concurrent LAN-free sessions as you have
tape drives available.

>With serverfree where the TSM server talks to the ESS/shark
>directly, how does TSM get things that are inconsistent
>like database files that have potentially changes in
>memory? 

It doesn't. Remember that LAN-free and server-free backups are available
for TSM's backup/archive client, but not for all of the specialty backup
clients such as TSM for Mail and TSM for Databases.

>Also, since TSM does not know the end platform,
>how can TSM backup files? Does it only back up blocks and
>the client must ask for enough blocks to make up the files
>it wants to restore?

The way that server-free backups happen is that TSM makes use of an
application like Tivoli's SANergy. SANergy creates an internal NFS
mountpoint with a chunk of SAN-attached disk that TSM's disk-based
storage pool uses and mounts the client's chunk of SAN-attached disk
onto that mountpoint. TSM backs up files across the mount. 

It makes for *fast* backups, since the bottleneck in this case is the
bus speed of the storage unit's disk controller. Metadata about the
backed-up files is sent from SAN disk to the TSM client (via fiber) to
the TSM server (via the LAN), but no data moves across the LAN or the
SAN.

--
Mark Stapleton