Also, are these RMAN backups?  If so, they use the API.  I'm not sure if
simultaneous write works for the API.  Anyone know?  Also, RMAN supports
multiple tape streams.  We are setup to use 4 parallel streams.  We used to
use physical tape, but now the backups just go to serial disk volumes
(devclass=file).  The DBAs here are happy with that.       ..Paul

At 06:14 PM 2/23/2009, Fred Johanson wrote:

The big gotcha here is that you cannot use the simultaneous write feature
if the backup is going lanfree.

________________________________________
From: ADSM: Dist Stor Manager [ADSM-L AT VM.MARIST DOT EDU] On Behalf Of Kelly
Lipp [lipp AT STORSERVER DOT COM]
Sent: Monday, February 23, 2009 1:28 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] backups direct to tape

Gill,

I will start by asking: What do you think happens?  The cool thing about
TSM is it will usually do what you think it will do.  If a tape error
occurs, the current transaction (whatever it happens to be) will fail.
What that means will vary.  In the case of a client/agent backup, a write
error on a tape will cause TSM to mount another tape and restart the
failed transaction. Data integrity is the hallmark of the product.

Direct to tape backups are actually cool. In fact, you can write two tapes
simultaneously: the onlinepool and the drpool volumes.  This avoids having
to migrate data from disk to tape and having to back that data up.  In the
case of a 500GB database that will reduce the amount of data flowing
through your server from 1.5TB to 500GB.  Huge savings.  And the write to
two tapes happens at the same speed as to one.

Kelly Lipp
CTO
STORServer, Inc.
485-B Elkton Drive
Colorado Springs, CO 80907
719-266-8777 x7105
www.storserver.com


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Gill, Geoffrey L.
Sent: Monday, February 23, 2009 11:28 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] backups direct to tape

I have a question that I hope those using TSM to back up direct to tape
can answer. We don't, and never have, done this here and I'm not looking
to implement it either. I am really looking for information as to "what
happens to the backup" is a tape error occurs. (I just know I'm going to
get this question when the dba's who have convinced everyone netbackup
and direct to tape is so great) I am interested too if the TSM agents
have the ability to compensate for this compared to a standard client
backup. Will the agent take this into consideration and continue the
backup with a different tape or will it die? The same question applies
to the standard backup.



Thanks for your help.





Geoff Gill
TSM Administrator
PeopleSoft Sr. Systems Administrator
SAIC M/S-G1b
(858)826-4062 (office)

(858)412-9883 (blackberry)
Email: geoffrey.l.gill AT saic DOT com

--
Paul Zarnowski                            Ph: 607-255-4757
Manager, Storage Services                 Fx: 607-255-8521
719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 AT cornell DOT edu