In regard to: Re: [Networker] Large File system issues, Roy Kidder said (at...:

>At home, I have a 269G file system (linux ext3) which I back up. At work,
>I have several which approach 1TB, including NTFS, UFS, HFS, and ext2/3.
>At work, I have a silo with 4 drives, so I don't have to manually swap
>any tapes, which is really the only issue I see with a large file system.

I thankfully haven't had any single filesystems hit the TB range yet, but
we do have several in the 300-600 GB range.

Roy, I would be interested to know if you've ever had to restore one of
your 1 TB fses, and if so how long it took.

I have had to do disaster recovery for a client on a couple different
occassions, but the largest volumes were only in the 40-60 Gig range,
thankfully.

>> hello all.
>> one of our business requirements demands a huge filesystem ~ 250 GB.
>> Does anyone here have any experience with backups/restores of a
>> filesystem
>> that big?

Atif, you don't say what kind of data will be on that filesystem.  It
makes a huge difference.  If the 250 GB is primarily large files, backups
and restores will be easier than if the 250 GB is lots and lots of small
files.

>> Are there any issues anyone can think of that I should consider?

Sure, the #1 issue you need to consider is this:  If I ever have to recover
this filesystem from scratch, what is the maximum amount of time it can
take to recover it?

Remember, users don't care at all about backups.  They only care about
restores.  ;-)  When planning for something like this, you kind of need
to work backwards.  Start by figuring out how long you can be without the
data (how long you have to recover that volume in the event of a problem
with the volume itself).

Once you know how long you have to perform the restore, you then need to
calculate (and test) how long it takes to recover that amount of data
in your environment.  As Roy said, network speed will be a big factor, but
there are lots of other factors too.

If the data doesn't change very often, or only small amounts of it changes
every day, you might be tempted to do something like a "once a month full,
incrementals the rest of the month".  If you have a disaster on the 28th
of the month, though, you could possibly be restoring data from 20 or
more tapes.  That's going to cut into your restore time significantly.

Again, if the 250GB is a "few" large files, it will backup and restore
much faster than if it's 1.5 million small files.

Only when you know how long you can take to recover the data, and the
factors (in and of your environment) that will impact that recovery time
will you know if you are going to have to jump through extra hoops to
meet those needs.

>> Also, we might be able to survive with 80GB fs. Any thoughts on that?

In general, smaller filesystems (even if there are more of them) are
easier to back up and restore to in a timely manner than larger
filesystems, but there are a *lot* of factors to consider.  One 250 GB
filesystem might be fine for backups and restores, in the right
environment.

Tim
--
Tim Mooney                              mooney AT dogbert.cc.ndsu.NoDak DOT edu
Information Technology Services         (701) 231-1076 (Voice)
Room 242-J6, IACC Building              (701) 231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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