One last question, backups

[Preston Crawford]

One last question. I've been tasked with setting up backups. Generally
I've done typical monthly/bi-weekly or weekly full backups with
incrementals rotating every six months or something. The current
organization I'm helping wants the following out of their backups. They
want incremental backups that only backup changes to files but don't
remove files that have been removed (in case they want to go back to
them). Is this possible? I thought an incremental backup would pick up a
deleted file and consequently delete it from that current backup. I don't
believe there's any way to do this. Am I right?

Preston

 

[Enkidu]

One last question. I've been tasked with setting up backups. Generally
I've done typical monthly/bi-weekly or weekly full backups with
incrementals rotating every six months or something. The current
organization I'm helping wants the following out of their backups. They
want incremental backups that only backup changes to files but don't
remove files that have been removed (in case they want to go back to
them). Is this possible? I thought an incremental backup would pick up a
deleted file and consequently delete it from that current backup. I don't
believe there's any way to do this. Am I right?

No, you are wrong. Say the file is in the full backup set taken on
Friday. On Monday it has not been changed so it is not backed up. On
Tuesday it is deleted. On Wednesday they want it back and it is in the
Friday's full backup.

If another file does not exist on Friday it is (obviously) not in the
Friday backup, but if it is created on Monday it is in the Monday
incremental backup. If it is deleted on Tuesday, and required on
Wednesday, it can be recovered from the Monday incremental.

Cheers,

Cliff

 

[Preston Crawford]

No, you are wrong. Say the file is in the full backup set taken on
Friday. On Monday it has not been changed so it is not backed up. On
Tuesday it is deleted. On Wednesday they want it back and it is in the
Friday's full backup.

If another file does not exist on Friday it is (obviously) not in the
Friday backup, but if it is created on Monday it is in the Monday
incremental backup. If it is deleted on Tuesday, and required on
Wednesday, it can be recovered from the Monday incremental.

I know it will be in the full backup. I probably didn't phrase the
question right (because it's kind of an odd request). They want the backup
to be performed in such a way that if the file gets deleted Monday, let's
say, the incremental backup won't pick that up. It will only pick up files
that have been modified. The deletion then, won't effectively be picked up
until the next full backup. All the while Monday, Tuesday, Wednesday,
Thursday, Friday, etc. will carry the file over (not even sure how that
would happen, maybe if you were using the same backup tape and the tape
was versioning the files or something) that was deleted Monday and not
kill it until you do the next full backup. Hopefully that makes sense.
It's a confusing thing they're asking for and I don't think it's doable.

Preston

 

[Matthew Miller]

Sounds to me that this is being asked so that whomever needs to restore a
file, will not have to figure out what tape is needed, instead, all files
would be available on the tape that ran the previous night. I am sure that
EMC or CA would be happen to sell you some solution that is outrageously
priced. however, to keep things relatively inexpensive, you are stuck with
the backup methods built into most systems; that is
incremental/differential/full. The users will simply need to be trained on
how to identify, from the backup software what tape is needed.

Another, potential solution would be Shadow Copy [if 2003 Server is being
used]. I have not had a chance to fully test and understand how shadow copy
works, but it may be worth looking into.

Matt

 

[Enkidu]

I know it will be in the full backup. I probably didn't phrase the
question right (because it's kind of an odd request). They want the backup
to be performed in such a way that if the file gets deleted Monday, let's
say, the incremental backup won't pick that up. It will only pick up files
that have been modified. The deletion then, won't effectively be picked up
until the next full backup. All the while Monday, Tuesday, Wednesday,
Thursday, Friday, etc. will carry the file over (not even sure how that
would happen, maybe if you were using the same backup tape and the tape
was versioning the files or something) that was deleted Monday and not
kill it until you do the next full backup. Hopefully that makes sense.
It's a confusing thing they're asking for and I don't think it's doable.

Backups are independent files. A full backup backs up all files. An
incremental backs up changed and new files. A changed file may be
changed from the last incremental or changed from an earlier
incremental or even the last full backup.

If a file is backed up in the original backup and is subsequently
deleted, it can be recovered until the original backup is overwritten.

If a file is created before an incremental, it is backed up in the
next incremental. It can be recovered from an incremental that
includes it until that incremental is overwritten.

If a file is created and deleted between backups it won't be included
in any backup.

Files are not "carried over" from tape to tape. Files will be included
in a tape only if they are created or modified between backups.

Think of it as "A full backup backs up all files" and "An incremental
backs up changed and new files".

If a file is modified several times during the week there will be
various versions in various backups, full and incremental. ANY of
these version can be restored.

Cheers,

Cliff