Re: [PLUG] RAID Backup Server

["William H. Magill" <magill@mcgillsociety.org>]

On 31 Oct, 2005, at 11:41, Pat Regan intoned:
> Backups to disk are good protection from accidental file deletion, and
> they make a good staging area for writing real backups to be sent off
> site.  As far as protection from hardware failure, they aren't much  
> more
> than a "delayed RAID."

Amen.

The biggest issue with any "backup" solution has nothing to do with  
creating the backup.

Backup of individual files is solely for their recovery in case of  
deletion.

Backup of a "System" requires that you be capable of restoring the  
SYSTEM to working order as of when the last backup was taken. A  
System is composed of many files.

If a System is well crafted, ALL user data is stored on devices  
independent of system data. With today's big disks that can result in  
a lot of wasted space... and the temptation to use it.

The primary issue is -- how long is it going to take you to return  
things to the way they were "before" you lost the system?  A 1-TB  
data store takes A LONG TIME to restore!

I realize that I'm talking about serious redundancy here, but Mark's  
questions are the minimum you need to consider when putting together  
a "backup solution."

File oriented backups are good for 99% of the time. But that last 1%  
is when you loose your business because you have to rebuild the  
entire system, and it suddenly turns out to take a couple of weeks,  
instead of a couple of hours.

One other thing to consider about Redundant Storage systems, not to  
be confused with RAID other than 1+0 (if I remember the RAID numbers  
correctly), when you are writing bad data to two locations  
simultaneously, both locations have bad data! Then you are forced to  
recover from your Archival Storage.

With today's disks, it IS perfectly reasonable to craft a "backup  
system" which uses removable disks (i.e. "bricks") instead of tapes.  
But, such a solution isn't cheap.

One last point about a "home grown" solution -- It's called the "bus  
question."
The question to ask?

"What happens when the architect gets hit by a bus?"

T.T.F.N.
William H. Magill
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magill@mcgillsociety.org
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