Backup software for a home network?

[Neil Maxwell]

So setting the backup type to "Full" will overwrite the target file if
it already exists?
Yes.

And if the existing incremental backups are referencing a full backup
that doesn't exist, they will be overwritten when the scheduled
incremental backup runs? In my experience, a scheduled incremental
backup will never overwrite an existing file, but maybe the conditions
just weren't right?

This is just my experience with TI7; my earlier experiences were with
tape-based backup and didn't have the same level of filename control.
Other programs may work differently.

When TI7 runs an incremental backup, it appends to the most recent
backup (full or incremental) and increments the file name. For
instance, if you don't do a full for 2 weeks and do incrementals, it
will get up to C-Full14.tib. If you then restart the full/weekly
series, it will replace C-Full.tib on the first full backup, then
replace C-Full2.tib thru C-Full7.tib on the following incrementals,
and start over again. It will leave the 8-14 files in place as
orphans, where they will get increasingly stale, and need to be
deleted to free up the space.

If, on the 3rd day, you ran another C-Full.tib full backup, the next
day's incremental would be named C-Full2.tib, and so on. All the
older files would still be there, but would be orphaned, and
eventually overwritten as the schedules got re-synced.

I see this when my full backups get missed for various reasons.
Deleting the orphaned incrementals depends on their creation date;
anything created before the full can be deleted, anything created
after the full is part of the current backup set, regardless of name.


Neil Maxwell - I don't speak for my employer

 

[Neil Maxwell]

I recommend considering a differential backup instead of an
incremental backup.

TI7 only offers what they call an incremental backup, which is the
same as a differential backup. This only backs up new files, and my
experience is that the incremental does not grow in size daily and is
often smaller than a previous day's.

The differential backup does not clear the archive bit, and therefore
you backup the same files each day plus any new ones that need to be
backed up. The advantage is that you only have one backup file.

TI7 treats the entire thing as a single backup. That is, when you
open a backup, it opens the most recent version - the full plus all
incrementals. It won't allow you to open up just a incremental.
There are multiple files, but it makes them one virtual backup. Their
big push is ease of use and wizards, and you lose some of the control
and granularity of traditional backup proggies. I haven't tried
deleting one of the incrementals to see how it would handle it; this
would be a good test.

Incremental backups are great if only a few files require backup each
day. But I have discovered from experimentation that the same large
files show up for backup each day, so why carry each day's backup on
disk? Also a differential backup is much easier to restore.

I backup the disk with Drive Image Pro, which does nothing to the
archive bit. Then I run an incremental backup to clear the archive bit
on as many files as I can. From there I run a diffierential backup
each midnight using Backup Exec that comes with Win2K (called
"NTBackup"). I only have one backup file to deal with.

Lots of techniques, as always. I like TI7 because of its simplicity
and friendliness, and have had very good luck using it to support
non-technical people. I haven't played with DIPro, but my experiences
with Ghost have left me unsatisfied. It does some stuff that TI7
doesn't, but at the cost of complexity, reboots to DOS, a much higher
level of geekiness, and the occasional "operating system not found"
error...


Neil Maxwell - I don't speak for my employer

 

[Bob]

TI7 only offers what they call an incremental backup, which is the
same as a differential backup.

Wrong.


--

Map Of The Vast Right Wing Conspiracy:
http://www.freewebs.com/vrwc/

"Welfare's purpose should be to eliminate, as far as
possible, the need for its own existence."
--Ronald Reagan

 

[Neil Maxwell]

Wrong.

Care to expand?


Neil Maxwell - I don't speak for my employer

 

[Bob]

Care to expand?

An incremental backup clears the archive bit. A differential backup
does not clear the archive bit.

With an incremental backup, you backup only those files that have been
modified since the last full or incremental backup. That's because
only those files have had their archive bet set by the act of
modification. This results in one backup file per incremental backup,
so if you do 7 incremental backups in a week, you will have 7 backup
files. Restoring is an arduous procedure because you have so many
backup files to deal with.

With a differential backup, you backup those files that have been
modified since the last full or incremental backup. However, since the
archive bit is not cleared, you back those same files up (and any
newly modified files) each time you do a differential backup. This
results in only one backup file, the most current one. There is no
need to keep the older backup files because the latest one contains
everything that was in the older ones (plus any newly modified files).
Restoring is an easy procedure because you only have one backup file
to deal with.

If you discover that the size of an incremental backup is not changing
much, then you should use differential backup because the same files
are being modified between backups. That is what I found out with my
Win2K system (which includes a "system archive"). If the same files
are being modified each time between backups, then why save the old
backups - they are basically the same each backup so all you would be
doing is cluttering your disk with redundant information.

I do a disk copy to a removable hard disk with Drive Image Pro. Then I
run one incremental backup to clear the archive bits because DIP
doesn't do that. Thereafter each Midnight I do a differential backup
putting the backup file on the same partition. That way when I create
the next DIP disk copy I have everything in one place. If I have to
restore the disk copy, I do that first then run the restore procedure.

I have actually had to do that a couple times recently thanks to
Microsoft's decrepit "updating" service crapping all over Win2K. The
procedure was pretty much seamless.


--

Map Of The Vast Right Wing Conspiracy:
http://www.freewebs.com/vrwc/

"Welfare's purpose should be to eliminate, as far as
possible, the need for its own existence."
--Ronald Reagan

 

[Neil Maxwell]

An incremental backup clears the archive bit. A differential backup
does not clear the archive bit.

(balance of good explanation snipped)

I probably should have stated that it's *essentially* the same as a
differential backup for TI7. You're right, they don't clear the
archive bit, and they do call it an incremental backup, but it behaves
very much like a traditional differential backup except for those
aspects.

Only changed files are backed up. If a full backup is performed on
Monday and a file changes on Tuesday, it gets backed up on Tuesday
night's backup. It does not get backed up again on subsequent days
unless it gets changed again, but the archive bit is left as it was
(TI7 doesn't ever change the archive bits, AFAIK, but uses internal
data to determine the file state). As I said, the incremental often
gets smaller as the week progresses, just like a differential file
might.

TI7 also restores everything as a virtual single file, regardless of
how many actual incremental files it has made. It restores the state
of the HD as of the last incremental backup in one operation
automatically. You can't choose the individual backups, which may not
be optimal for some uses, but is very simple and bulletproof.

It's really not a traditional backup program, which is one reason I
like it, after many years of using backup programs. It's very easy to
support with inexperienced users, and the focus of the program is
user-friendly wizards and simplicity. As long as it supports your
hardware, I've found it to be reliable, fast, and very easy.

I consider it a bit of a revolution in HD backup, and have helped a
number of inexperienced users set up backup systems with it. So far,
it's worked very well for both backup and restore, but time will tell
on long-term reliability.


Neil Maxwell - I don't speak for my employer