Re: backup solution

mechdan_at_yahoo.com
Date: 08/28/05 

Date: 27 Aug 2005 15:08:01 -0700

Jean-David Beyer wrote:
> John-Paul Stewart wrote:
> > mechdan@yahoo.com wrote:

> >> Unless you have a very compelling reason to still use tape
> >> backup, backup to hard drives is cheaper, faster, more robust,
> >> and far more flexible. Naturally, if you are concerned about
> >> a power surge corrupting ALL hard drives at once, you may want
> >> to use some removeable hard drives.

> Of course, by Murphy's Law, a power surge, lighting strike, home fire, or OS
> going mad, will do just that.

Small nit--an OS going mad might kill all of the hard drives
in one computer, but not all of the hard drives in a reasonably
set up network with a backup server. Neither a backup server
nor the machines it is backing up need anything more than
read access to each other's data.

> Are hot swappable hard drives now cheaper than
> tape cartridges?

Yes. The cheapest hot swappable solution is a USB2.0->IDE
adapter or enclosure. Standard inexpensive IDE hard drives
are used. The entire set of backup drives and USB adaptors
may cost less than even a single tape drive (not even
counting the tapes yet).

> > In order for the backup to of any use at all, removable media is a
> > *must*. So is having multiple generations of backup available. If your
> > lone backup is being over-written with a newer backup at the time of a
> > catastrophic failure, you're sunk. It doesn't matter if you're using
> > tape or removable hard drives, you need more than one set of backup
> > media.

You don't need separate media. Even with the most brain-dead of
backup solutions--manually copying a directory, you can have
multiple copies from different days on the same partition.
As it is, any half-decent backup solution allows for incremental
backups that allow multiple "virtual" backups of different days,
without the wasted space of duplicate copies of unchanged files.

> > Likewise, you need to be able to physically move your backup off
> > site (think flooding, fire, etc.).

That's what computer networks are for. You don't necessarily need
so much bandwidth devoted to backups since only changed file blocks
need be transmitted.

> That is for sure. That is why I have 23 tapes for each machine.

> Monday, Tuesday, ..., Saturday
> First Sunday, Second Sunday, ..., Fifth Sunday
> January, ..., December

Wow, that's mind boggling overkill! How many machines do you
have? I'm imagining hundreds or thousands of tapes.

>This way, if I stupidly mess up or delete a file, and discover it
>immediately, I can recover a copy under 24 hours old. If I do not notice for
>about a week, I can get one under a week old, and if I do not notice for
>almost a month, I can get one under a month old, and if almost a year goes
>by, I can get one under a year old.

Any sort of incremental backup system can do much the same with
hard drive backups, while consuming much less space and
requiring much less time and effort to recover specific data.

But it's better--anyone can browse and restore their own old
files, without any attention from the system administrator.
If the user isn't sure how far back he needs to go in order
to get the desired version of his files, he can browse them
at his leisure without requiring a system administrator to
manually go through a bunch of tapes.

>I keep all but the current tape in a different room from the computers, and
>the monthly tapes in the safe deposit box at the bank. I sure would not want
>want to buy 46 hot swappable hard drives or store 24 of them at my bank.

I don't see why even the current tape needs to be in the same
room as "the computers".

It seems to me that you could accomplish much the same thing as
what you're doing now with only a few hard drives--two+ "live"
mirrors in a backup server (in a different room as the other
machines, if you like), and two+ in storage at the bank. Every
month or so, half of the hard drives in storage at the bank are
taken out so they can be synchronized with one of the "live"
drives (e.g. with rsync).

I'm assuming that it only takes one "live" drive to store all
of the desired backups for all of the machines (using incremental
backup techniques).

> > Personally, I find the compelling reasons to use tape are the easy
> > ability to have multiple sets of backup media and its portability.

Isaac Kuo

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