Hello all.  When I saw this posting I was tempted to reply but knowing I
had a DR test coming in mid-NOV I figured I'd get some real life data about
DIRMC to share with everyone.  I was not prepared for what happened.

Background:

Server TSM4.1.1 on AIX 4.3.3.6
Client TSM4.1.1 on AIX 4.3.3.6
I have DIRMC specified for all clients.   The structure is as follows:

DIRMC:  uses pool DIRDISK which migrates to pool DIRTAPE,    backed up to
pool DRTAPES
DATAMC:  uses pool DATADISK which migrates to pool DATATAPE,  backed up to
pool DRTAPES

The result is a single copy pool containing all data and dir info (non
collocated).


DR RESULTS:

Having restored ONLY the TSM server db and log areas, I updated all vols in
DIRTAPE and DATATAPE to destroyed.  Also updated all disk vols to off-line.
Then updated all tapes in DRTAPES to READO.

When I issued a restore for any given FS, all of the dirs were recreated
(restored) WITHOUT any tapes being called for.  The first mount didn't
occur until a data file was needed.

Signed confused.    :-<

PS.  Send light




                    Jochem van
                    Hal                  To:     ADSM-L AT VM.MARIST DOT EDU
                    <jvhal@ALLSHA        cc:
                    RE.NL>               Subject:     DIRMC - disadvantages 
only?
                    Sent by:
                    "ADSM: Dist
                    Stor Manager"
                    <ADSM-L AT VM DOT MA
                    RIST.EDU>


                    10/25/00
                    10:43 AM
                    Please
                    respond to
                    "ADSM: Dist
                    Stor Manager"






Hi all,

The 'old' redbook "Getting started with ADSM: A practical Implemantation
Guide" recommends to use a seperate MC and STP for directories (for restore
performance reasons).  Chapter 13.2.3 DIRMC (page 236) states:

"In a restore ..., ADSM first restores the directories and then the
files..."

(This chapter is identical in the newer "Getting started with TSM:
Implementation Guide.)

However there are DIRMC disadvantages as well; recently a known DIRMC
performance problem was described by NORBERT WINDRICH:

>we made a move data of a dirmc copy pool. The move data process
>needs 5:12 hours to move 70 823 172 bytes. Most of the data is read
>from a disk storage pool. For database files we can move up to 10 GB
>per hour.


At out site we have the same problem (caused by tape repositioning zillion
times) , but with migration.  Fortunately BILL BOYER responded with the
following AND a solution:

>A co-worker of mine worked with IBM/Tivoli on this. The symptoms came
during
>the reclamation of the offsite copypool tapes for the DIRMC disk storage
>pool. The answer he got was that reading from the disk storage pool was
done
>a file at a time and not buffered. They said it was because it was a
random
>access device and they had no plans to 'fix' it.[...]
>What he came up with was to create a sequential primary pool with a FILE
>device class and make this the NEXTSTGpool for the DIRMC disk pool and
>migrate daily. The reclamation and BA STG are alot faster.[...]
>The reclamation [...] runs in about an hour [...] instead of a day.


This solution sounds perfect and should work (not repeated yet), but ... is
there still a need for DIRMC after RICHARD SIMS kicks in?:

[...]
>    Consider also that dirmc isn't what it once was.  ADSMv3
>introduced the concept of Restore Order.  See that entry in
>http://people.bu.edu/rbs/ADSM.QuickFacts, or APAR IC24321.

So, i looked up this entry in the QuickFact to find (try to find this in
the
TSM manuals...):
                                        [...]"restore order" considers
where objects
                                        exist on sequential media and
brings
                                        them back in this order so that the
                                        media can be moved from beginning
to
                                        end.  One of the side effects of
this[...]

This suggest that (in V3) files and directories are retrieved just as the
come along on the media, contrary to the redbook suggestion ("In a restore
..., ADSM first restores the directories and then the files..."), however
the APAR text is not completely clear to me. If the redbook is correct, a
seperate pool for DIRMC makes sense.  If the redbook in not correct, it
seems there is no justification for a DIRMC pool.

In the last case we would all be better off just leave the
complicated-but-not-so-usefull feature!

This leaves me with two Questions:

1) Is the use of DIRMC obsolete? (complex, but no advantage) (of course we
can always 'make up' some advantage, like 'its nice tho have the dirtree
seperate..')

2) If the redbook is incorrect, but if DIRMC is still used (with seperate
STG) how will a restore work, first the DIRMC STP, then the file STP or
what?



Allshare Personnel BV

Jochem van Hal


mailto:jvhal AT allshare DOT nl
www.allshare.nl

tel +31 (0) 23 569 22 21
mob +31 (0) 6 21 588 423
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