As has been noted already, subfile backup was originally targeted mainly
for remote workstation/laptop users coming in over slower network
connections. Most of these users (so we thought) would not be dealing with
such large files. While subfile can technically be used in higher
bandwidth networking environments or on server-class systems, this was not
the target TSM client type for subfile backup.
The subfile cache contains "reference" files, not necessarily
byte-for-byte copies of the original file.
- If the file is smaller than 1 KB, it is deemed to small to make subfile
worthwhile, so the whole file gets backed up.
- If the file is larger than 2 GB, it is deemed too large for subfile, so
the whole file gets backed up. In theory the upper size limit could be
raised, but the work involved is bigger than a breadbox and not in plan at
this time.
So in the above cases, no reference file is created in the subfile cache.
OTHERWISE...
- If the file is under 3 MB, the reference file will include a
byte-for-byte copy of the original base file.
- If the file is larger than 3 MB, "block signatures" are used to create
the reference file, to keep it to a smaller size. it is NOT a
byte-for-byte copy of the file.
Regards,
Andy
Andy Raibeck
IBM Software Group
Tivoli Storage Manager Client Product Development
Level 3 Team Lead
Internal Notes e-mail: Andrew Raibeck/Tucson/IBM@IBMUS
Internet e-mail: storman AT us.ibm DOT com
IBM Tivoli Storage Manager support web page:
http://www.ibm.com/software/sysmgmt/products/support/IBMTivoliStorageManager.html
The only dumb question is the one that goes unasked.
The command line is your friend.
"Good enough" is the enemy of excellence.
"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> wrote on 02/13/2008
09:04:31 PM:
> Yes, files larger than 2 GB are backed up individually when you have
subfile
> backup turned on.
>
> However (don't shoot the messenger here), I'll save you some time and
> confusion by pointing out that you aren't going to get any significant
> benefit from implementing subfile on a large file server.
>
> Subfile backup was designed to work on laptops, not servers.
>
> The "base" or initial backup copy of a file is stored in a cache
directory
> on the client, which is also limited in size to 2 GB. TSM uses the base
> file to calculate the changes or "delta", and sends the delta only (the
> subfile) on subsequent backups.
>
> But once you exceed 2 GB of backed up files in the cache, older files
(LRU)
> are purged from the cache. When they change and need to be backed up
> again, it is a regular backup, not a subfile.
>
> In short, you can only manage a total of about 2 GB of files for subfile
> backup, and only files less than 2 GB in size are eligible.
>
>
> On 2/13/08, Sam Sheppard <SHS AT sddpc.sannet DOT gov> wrote:e
> >
> > ---------------------------- Top of message
----------------------------
> > >>--> 02-13-08 16:06 S.SHEPPARD (SHS) Re: Backing up PST
files
> >
> > We are in the same boat here but, even worse, the customer has
'chosen'
> > to store all of the .PST files on a shared NetApp FAS drive, something
> > not officially supported by Microsoft. Supposedly this was only going
to
> > be a temporary solution until implementation of something called
> > Symantec Enterprise Vault. However, the $1M price tag on that is now
> > a problem and we have been asked the implications of continuing to do
> > these backups as we do now, given a 1TB/year growth rate.
> >
> > Currently, we are backing up around 400GB/night out of 2TB of .PSTs
and
> > were going to setup a test of subfile backup early next week. I too
> > would be interested in any limitations to this scheme. If there is a
> > .PST larger than 2GB, is it backed up normally?
> >
> > Thanks
> > Sam Sheppard
> > San Diego Data Processing Corp.
> > (858)-581-9668
> >
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> >
> >
> > ---------------------------- Top of message
----------------------------
> > >>--> 02-13-08 10:43 ..NETMAIL (001) [ADSM-L] Backing up PST
f
> > Date: Wed, 13 Feb 2008 12:41:56 -0500
> > From: "Paul Zarnowski" <psz1 AT CORNELL DOT EDU>
> > Subject: [ADSM-L] Backing up PST files using dynamic subfile and OFS
> > To: ADSM-L AT VM.MARIST DOT EDU
> >
> >
>
_________________________________Top_of_Message_________________________________
> >
> > Greetings...
> >
> > We are starting to use Exchange and Outlook here, and now we need to
> > figure
> > out how to backup PST files.. I know there has been some discussion
of
> > this in the past on this list, and I have researched this. Here's our
> > problem.
> >
> > We have a client constituency who will be running Outlook on systems,
some
> > of which are connected sporadically (laptops) and/or over slower speed
> > network connections.
> >
> > It seems that Open File Support (OFS) can be used to successfully back
up
> > PST files, which is good. We'd like to also use dynamic subfile
backup on
> > the systems that are connected via slower networks. The problem is
that
> > subfile backups have a 2GB filesize limit, and PST files can grow
> > >2GB. Is
> > anyone else faced with this challenge? If so, how are you addressing
it?
> >
> > Thanks.
> > ..Paul
> >
> >
> > --
> > 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
> >
> >
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> >
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