Subject: RE: Backup Software Question

From: Jürgen Weltzer <[email-masked]>
Date: Mon, 30 Jul 2001 12:42:34 +0200

I make it like this:
buying a second PC - with linux, netatalk and a hard drive like the 
server volume.
With "copydir" (from freshmeet) (the package is called "mirrordir") 
and cron all my files are backuped automaticly every night - older 
versions are kept for some days (you can define it in seconds).
-- 
Viele Grüße
Jürgen Weltzer

- - - - - - - - - - - - - - - - - - -
Werbeagentur Weltzer
Max-Eyth-Straße 8
71065 Sindelfingen
Tel. +49 (0) 70.31.81.32.31
Fax +49 (0) 70.31.81.16.01
http://www.w-ww.de/
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Mit am besten lernt man die Menschen kennen, indem man sie beobachtet,
wenn es irgendwo etwas gratis gibt. (A.L.)

---

From: Christian Schmidt <[email-masked]>
Date: Mon, 30 Jul 2001 22:52:13 +0200

>  versions are kept for some days (you can define it in seconds).

Well, a backup stored on a HD isn't a real backup IMHO, is it?
What if your backup-HD crashes?

Yours,
Christian
-- 
Christian Schmidt
[email-masked]

---

From: Chris Garrigues <[email-masked]>
Date: Mon, 30 Jul 2001 16:15:47 -0500

> From:  Christian Schmidt <[email-masked]>
> Date:  Mon, 30 Jul 2001 22:52:13 +0200
>
> J=FCrgen Weltzer wrote:
> 

what if your tape becomes unreadable?

How is a backup on a hard disk not a backup?

chris

-- 
Chris Garrigues                 http://www.DeepEddy.Com/~cwg/
virCIO                          http://www.virCIO.Com
4314 Avenue C                   
Austin, TX  78751-3709		+1 512 374 0500

  My email address is an experiment in SPAM elimination.  For an
  explanation of what we're doing, see http://www.DeepEddy.Com/tms.html 

    Nobody ever got fired for buying Microsoft,
      but they could get fired for relying on Microsoft.

---

From: Rich Lafferty <[email-masked]>
Date: Mon, 30 Jul 2001 17:24:04 -0400

> what if your tape becomes unreadable?

Then you get the tape from the (day, week, month) prior from offsite
storage. How many hard drives are you planning on buying?
 
> How is a backup on a hard disk not a backup?

Well, it's not particularly useful for disaster recovery, only for
recovering from user error, and the usual goal of a backup plan is to
insure against data loss from both disasters and user error. Disaster
recovery tends to be the one that's crucial to keeping a business running,
though, and it's also the trickier one to manage, so it tends to get
priority, at least in an enterprise setting.

  -Rich

-- 
Rich Lafferty --------------+-----------------------------------------------
 Montreal, Quebec, Canada   |  "Do not dangle the mouse by the cord or
 http://www.lafferty.ca/    |   throw it at coworkers."  -- SGI Indy manual
[email-masked] -----------+-----------------------------------------------

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From: Chris Garrigues <[email-masked]>
Date: Mon, 30 Jul 2001 16:40:29 -0500

> From:  Rich Lafferty <[email-masked]>
> Date:  Mon, 30 Jul 2001 17:24:04 -0400
>

We have a raid array at a co-location point to which we back up incrementals 
for our customers.

I can recreate a customer machine on fresh hardware and drive it to his office 
faster than he could read the most recent full plus incrementals off of tape.

Chris

---

From: Harald Wagener <[email-masked]>
Date: Tue, 31 Jul 2001 10:47:02 +0200

> > Date:  Mon, 30 Jul 2001 22:52:13 +0200

[snip]
> what if your tape becomes unreadable?

well, too bad, I hope You check Your backups regularly for consitstence and 
functionality.

There are numbers for stuff like how often can a tape be written to and read
from(depends on the model).

> How is a backup on a hard disk not a backup?

It's not a _real_ backup. It's a redundant storage with identical points of
failure. Since hard discs are random access media, they can also be randomly 
deleted. This is harder with tapes that are handled properly, i.e. stored in a
fire proof water sealed safe off site. 

Secured tapes, even if they are stored in the same room as the machine being
backed up, are also less affected by power surges or other electrical
instabilities (as long as the sparks don't fly...). 

It is also easier to replace the read/write mechanism (i.e., the drive) when using
a tape backup solution than it is with a hard disk.

So, if You take care of Your backups, there is a significant decrease in Your
chances of losing data. Nothing of this is foolproof, nonetheless.

H.

-- 
Harald Wagener      |                                Systemadministrator 
FCB/Wilkens GmbH    |                              Tel.:+49-40-2881-1252 
An der Alster 42    |                              Fax.:+49-40-2881-1263 
20099 Hamburg       |                         http://www.fcb-wilkens.com

---

From: "Chris Garrigues" <[email-masked]>
Date: Tue, 31 Jul 2001 09:23:14 -0500

> From:  Harald Wagener <[email-masked]>
> Date:  Tue, 31 Jul 2001 10:47:02 +0200
>
> Chris Garrigues wrote:
> > 

I do.  This is easy to do on the RAID array where they live.

> fire proof water sealed safe off site. 

It's also harder to do when it's on an off-site RAID array to which the users 
only have read access.  I wouldn't consider it as having identical points of 
failure since it's on a different hard drive using RAID technology instead of 
single drive technology on a different computer system on a different (but 
also secured) network in a different building on a different power grid.

> a tape backup solution than it is with a hard disk.

Easier than replacing one hot-pluggable drive in a RAID array?

> chances of losing data. Nothing of this is foolproof, nonetheless.

This is certainly true, but it doesn't have anything to do with whether the 
media is tape or disk.

I just like not having to change tapes every day.  I also like my users being 
able to restore their files through a web interface that I wrote.

Chris

---

From: Danny Sauer <[email-masked]>
Date: Tue, 31 Jul 2001 09:56:53 -0500

> > > Well, a backup stored on a HD isn't a real backup IMHO, is it?
[...]
> fire proof water sealed safe off site. 
[...]

I'm using an off-site hard drive with rsync over ssh.  The most recent
web/mail server backup doubles as a can-be-made-live-immediately redundant
server, should the office lose connectivity for any reason (it's not
normally live, for security).  That gets rid of the single point of failure,
and allows the capability to minimize downtime should something bad happen
at the main site.  With enough space on the off-site backup server to hold
a yesterday, last week, and week-before-last backup (on seperate physical
drives), it serves our purpose of making restoration as quick as possible
and storage as easy to maintain as possible without having a single point
of failure.  Every once in a while, CD-R's are burned with the important
stuff (and stored in a firesafe), just in case something takes out the
backup's town *and* ours without killing everyone in our business too. :)

Just another approach that may give someone an idea, but probably not the
best choice for everyone...

BTW, "mount -o remount,rw /backup;backup.sh /backup;mount -o remount,ro /backup" will prevent random deletion. ;)

--Danny

---

From: Harald Wagener <[email-masked]>
Date: Wed, 01 Aug 2001 10:52:51 +0200

Chris Garrigues wrote:
> > > (by the way, I fon't think I wrote this, but the argument still holds true).

If You take systems safety as I learned it (I might be wrong, anyway), the
differences between a
hard disk and a RAID array can easily be seen if You draw a fault tree: the points
of failure are the same,
but in the RAID array failure of one disk is 'not critical'.
most important here is that there is a different network and a different power
grid.
Just to be nitpicking: The power grid is also served by another power
company/power plant?
I assume You have an UPS at hand, so this would weaken the criticality of this
point as well.

But this is entirely different than the scenario someone offered, where You have a
machine in hot standby that simply gets a copy of the original machine's hard disk
each night.

> Easier than replacing one hot-pluggable drive in a RAID array?

a hot pluggable drive in a RAID array is not the typical hard disk on a hot stand
by machine
(i.e. not everybody can afford a RAID system, even a second one just for the
prupose of backup systems).

> This is certainly true, but it doesn't have anything to do with whether the

By the way, it does. It depends on the MTBF of the media used. In Germany for
example, You need to store
financial data that has been digitally produced for ten years for the tax
collectors to check if You did everything right. 
print copies won't suffice from 2002 on. How many disks You use are older than 8
years? 12 years? 

Long term storage of magnetic tapes is a field well researched. Not even CDs come
close, if You remember the press about certain
fungi destroying cd's (in extreme weather conditions, they say today). It's also
true that it is often difficult to get tape readers that read tapes used ten years
ago (Your university might have one, but it probably won't work anymore).

Well, I think we can agree that if the storage used is significantly different
(the difference vector 
containing factors such as physical distance), the chances that Your backup
solution will help You
in disaster recovery will rise as significantly.

> I just like not having to change tapes every day.

That's the reason why automated libraries exist.

>  I also like my users being

And we would like our users not to delete their files in the first place (-: .
This cannot be technically prevented on the working set

As has been said before, different solutions serve different needs of different
people.

I am quite confident that Your solution works sweet for You. And I don't see my
point
being attacked by Yours. Your solution is an alternative to mine and covers the
most important
points needed to have a backup rather than a copy. If You want to discuss this
topic further, 
I suggest we do it off list since we are pretty much off topic right now.

Regards,
	Harald
 
>   ----------------------------------------------------------------------------------
>    Part 1.2Type: application/pgp-signature

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From: "Chris Herrmann" <[email-masked]>
Date: Thu, 2 Aug 2001 09:17:24 +1000

Hmm. methinks this looks like a private discussion, and not anything vaguely
related to netatalk.

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Harald Wagener
Sent: Wednesday, 1 August 2001 18:53
To: [email-masked]
Cc: [email-masked]
Subject: Re: Backup Software Question

If You take systems safety as I learned it (I might be wrong, anyway), the
differences between a
hard disk and a RAID array can easily be seen if You draw a fault tree: the
points
of failure are the same,
but in the RAID array failure of one disk is 'not critical'.
most important here is that there is a different network and a different
power
grid.
Just to be nitpicking: The power grid is also served by another power
company/power plant?
I assume You have an UPS at hand, so this would weaken the criticality of
this
point as well.

But this is entirely different than the scenario someone offered, where You
have a
machine in hot standby that simply gets a copy of the original machine's
hard disk
each night.

> Easier than replacing one hot-pluggable drive in a RAID array?

a hot pluggable drive in a RAID array is not the typical hard disk on a hot
stand
by machine
(i.e. not everybody can afford a RAID system, even a second one just for the
prupose of backup systems).

> This is certainly true, but it doesn't have anything to do with whether
the

By the way, it does. It depends on the MTBF of the media used. In Germany
for
example, You need to store
financial data that has been digitally produced for ten years for the tax
collectors to check if You did everything right.
print copies won't suffice from 2002 on. How many disks You use are older
than 8
years? 12 years?

Long term storage of magnetic tapes is a field well researched. Not even CDs
come
close, if You remember the press about certain
fungi destroying cd's (in extreme weather conditions, they say today). It's
also
true that it is often difficult to get tape readers that read tapes used ten
years
ago (Your university might have one, but it probably won't work anymore).

Well, I think we can agree that if the storage used is significantly
different
(the difference vector
containing factors such as physical distance), the chances that Your backup
solution will help You
in disaster recovery will rise as significantly.

> able to restore their files through a web interface that I wrote.

And we would like our users not to delete their files in the first place (-:
.
This cannot be technically prevented on the working set

As has been said before, different solutions serve different needs of
different
people.

I am quite confident that Your solution works sweet for You. And I don't see
my
point
being attacked by Yours. Your solution is an alternative to mine and covers
the
most important
points needed to have a backup rather than a copy. If You want to discuss
this
topic further,
I suggest we do it off list since we are pretty much off topic right now.

Regards,
	Harald