Re: restore question

Correction/clarification:

> TSM mounts each needed tape once and only once

A colleague has pointed out that this is not always true. A tape may be
mounted more than once if it contains portions of a file where the
beginning of the file is on another tape. For example, lets say that we
have several files that span across more than one tape:

FILEA begins on TAPE01 and continues on TAPE20
FILEB begins on TAPE02 and continues on TAPE20
FILEC begins on TAPE03 and continues on TAPE20

If FILEA, FILEB, and FILEC are restored, then TAPE20 will be mounted 3
times, like this:

- Restore FILEA: mount TAPE01 then TAPE20
- Restore FILEB: mount TAPE02 then TAPE20
- Restore FILEC: mount TAPE03 then TAPE20

So while TSM does indeed work to minimize tape mounts, it is possible for
a tape to be mounted more than once.

Regards,

Andy

Andy Raibeck
IBM Software Group
Tivoli Storage Manager Client Development
Internal Notes e-mail: Andrew Raibeck/Tucson/IBM@IBMUS
Internet e-mail: storman AT us.ibm DOT com

The only dumb question is the one that goes unasked.
The command line is your friend.
"Good enough" is the enemy of excellence.




Andrew Raibeck/Tucson/IBM@IBMUS
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
08/20/2003 05:54
Please respond to "ADSM: Dist Stor Manager"

        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        Re: restore question


"No query" restore has nothing to do with minimizing tape mounts for
restore. For a given restore, TSM mounts each needed tape once and only
once, and reads it from front to back.

The most visible benefit of no query restore is that data starts coming
back from the server sooner than it does with "classic" restore. With
classic restore, the client queries the server for all objects that match
the restore file specification. The server sends this information to the
client, then the client sorts it so that tape mounts will be optimized.
However, the time involved in getting the information from the server,
then sorting it (before any data is actually restored), can be quite
lengthy. No query restore lets the TSM server do the work: the client
sends the restore file specification to the server, the server figures out
the optimal tape mount order, and then starts sending the restored data to
the client. The server can do this faster, and thus the time it takes to
start actually restoring data is reduced.

In either case, for a given restore, TSM will restore the files and
directories in a manner that optimizes tape mounts. If it so happens that
a file is restored before it's parent directory is restored, then the
client will create the parent directory, restore the file, then restore
the parent directory when it encounters it in the restore sequence.

Regards,

Andy

Andy Raibeck
IBM Software Group
Tivoli Storage Manager Client Development
Internal Notes e-mail: Andrew Raibeck/Tucson/IBM@IBMUS
Internet e-mail: storman AT us.ibm DOT com

The only dumb question is the one that goes unasked.
The command line is your friend.
"Good enough" is the enemy of excellence.




Karel Bos <Karel.Bos AT NUON DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
08/20/2003 00:02
Please respond to "ADSM: Dist Stor Manager"

        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        Re: restore question


Hi,

Depends (love that statement) on the type of restore. If you have a
no-query
restore, the tsm server will restore the data in a "as few mounts as
possible way", if you have a query restore the client will ask the tsm
server for a object (being file or directory), so the TSM server can not
do
its thing to minimize the number of tapemounts.

>From the read.me:

No query restore
When you enter an unrestricted wildcard source file specification on the
restore command and do not specify any of the options: inactive, latest,
pick, fromdate, or todate, the client uses a different method for
retrieving
files and directories from the server. This method is called no query
restore because instead of querying the server for each object to be
restored, a single restore request is sent to the server. In this case,
the
server returns the files and directories to the client without further
action by the client. The client merely accepts the data coming from the
server and restores it to the destination named on the restore command

Regard,

Karel

> -----Oorspronkelijk bericht-----
> Van: i love tsm [mailto:ilovetsm AT HOTMAIL DOT COM]
> Verzonden: dinsdag 19 augustus 2003 21:02
> Aan: ADSM-L AT VM.MARIST DOT EDU
> Onderwerp: restore question
>
>
> Hi all
>
> A basic question...
>
> tapes are non collocated
>
> if you kick off a restore of multiple directories on a win2k
> client will TSM
> mount a tape and get all the data off that tape for the directories
> concerned then move on to the next volume, or does it restore
> sequentially
> one directory at a time, i.e it could mount the same tape
> numerous times as
> it goes through thr directories.
>
> Many Thanks
>
> _________________________________________________________________
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