[gpfsug-discuss] mmbackup with own policy

Ulrich Sibiller u.sibiller at science-computing.de
Thu Jun 24 11:24:30 BST 2021


On 6/23/21 11:52 PM, Wayne Sawdon wrote:
> At a higher level what are you trying to do? Include some directories and exclude others? Use a 
> different backup server? What do you need that is not there?

The current situation is that a customer insists on using different management classes on the TSM 
server for big files than for small files. We have setup additional server stanzas 
<backupserver>_big and <backupserver>_small representing the management classes.

servername         <backupserver>_small
...
inclexcl           .../dsm.inclexcl.small
...


# cat .../dsm.inclexcl.small
include ... smallfile

("smallfile" is the management class)

Now we need to run mmbackup against the <backupserver>_small and restrict ist to only treat the 
small files and ignore the bigger ones. As we cannot determine them by name or path we need to use a 
policy (.. WHERE KB_ALLOCATED < something)

> mmbackup is tied to Spectrum Protect (formerly known as TSM) and gets its include/excludes from the 
> TSM option files. It constructs a policy to list all of the files & directories and includes 
> attributes such as mtime and ctime. It then compares this list of files to the "shadow database" 
> which is a copy of what the TSM database has. This comparison produces 3 lists of files: new files & 
> files that have the data changed, existing files that only have attributes changed and a list of 
> files that were deleted. Each list is sent to Spectrum Protect to either backup the data, or to 
> update the metadata or to mark the file as deleted. As Spectrum Protect acknowledges the operation 
> on each file, we update the shadow database to keep it current.

Exactly. I am aware of that.

> So writing a new policy file for mmbackup is not really as simple as it seems. I don't  think you 
> can change the record format on the list of files. And don't override the encoding on special 
> characters. And I'm sure there are other Gotchas as well.

That's just what I wanted to express with my previous mails. It is not as simple as it seems AND it 
is not documented. We want to use all that fancy shadow file management that mmbackup comes with 
because it is sophisticated nowadays and generally works flawlessly. We do not want to reinvent the 
mmbackup wheel.

So for the current situation having a simple way to (partly) replace the WHERE clause would be of 
great help. I acknowledge that offering that in a general way could get complicated for the 
developers. Having a documentation how to write a policy that matches what mmbackup without -P is 
doing is the first step the improve the situation. My posted policy currently works but it is 
questionable how long that will be the case. Once mmbackup changes its internal behaviour it will 
break..

Uli
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