Re: [PLUG] RAID Backup Server

[bergman@merctech.com]

In the message dated: Mon, 31 Oct 2005 09:26:41 EST,
The pithy ruminations from Edmund Goppelt on 
<[PLUG] RAID Backup Server> were:
=> I want to build an inexpensive backup server with 1 terabyte storage.

Good idea.

=> Does anyone have any experience in this area?

Yes.

=> 
=> The server would store backups for my home and business networks.  The

Hmmm...

You can't see it from your angle, but over here, all sorts of warning lights 
and sirens are going off when I see the phrases "business networks"
"inexpensive" and "backup server" together.

Here are some questions I suggest that you consider before going any further:

	What's the value of this data to your business?

	What's the value of your personal data?

	Is it appropriate to combine the data from your home and business
	networks onto a single backup device. If you are sued, and the
	business records are siezed, is there personal data that you don't
	want to have co-mingled when the backup server is taken away?

	Is there data (financial records, for example), that needs to be kept
	for a long period of time?

	Is there a need to keep snapshots of data at specific points in
	time (for example, a backup made the night before the quarterly invoices
	are sent out may need to be retained--intact--for 60 days until all
	invoices are received)?

	How much data do you have?

	How has the amount of data changed in the past year?

	What's the "churn" (ie., the number and size of files that change)?
	For example, if you've got a 100MB database of customer orders, it may
	change very little in size (2~3KB) per day, but since the database
	itself changes, the whole thing may need to be backed up. It's amazing
	how quickly you can go through disk space on a backup device...

	Is there a need to keep successive versions of any data? For example,
	if you're developing software or CAD drawings, you might to be able to
	revert to a version that's several days old.

	What are your requirements for how long it can take to backup the
	data?

	What are your requirements for how long it can take to restore the
	data?

	What's the connection (network) between the different machines? You
	say "home and business networks". Are they physically distinct?

	What software do you plan to use to manage backups and restores?

	What's your budget? 

If possible, try to answer these questions before looking at the hardware. 
These requirements will go a long way to avoiding the common scene where 
someone picks nifty hardware out of a catalog and then calls if a backup 
solution. IMNSHO, backups are a whole lot more than just writing a copy of some 
bits to another disk...

=> server has to be able to handle a drive failure without loss of
=> data. As far as I know this means a RAID system of some sort.
=> 

Right.

=> My plan at this point is to roll my own linux based RAID system (i.e.,
=> buy 4 SATA drives and stuff them into an disk array):
=> 
=> 1 Addonics 4SA Disk Array:  $120
=> 4 Seagate Barracuda 250s @ $107:  $428
=> Linux server:  already have this, so no additional cost

Whoa! You're looking to achieve 1TB of (raw) storage, and using 4x250GB
drives. The acronym RAID means "Redundant Array of Inexpensive Drives". What
you're proposing has absolutely no redundancy...the drives will be essentially
concatenated together, to produce a single virtual 1TB drive. This will
increase the chance of failure, and a single failure will make the entire
array useless, with no chance of recovery.

At a minimum, to achieve any redundancy, you need a RAID-5 configuration. The
number "5" has nothing to do with the number of disks, but (coindicently),
you'd need 5x250GB disks.

>From my point of view, backup-to-disk only barely qualifies as a "backup
solution". It offers virtually no archive capability, it's very difficult to
send the data off-site, and has a high risk of failure, compared to
technologies like tape. Of course, it's cheap & easy.

Mark


=> 
=> Total Cost:  $548
=> 
=> $548 seems pretty reasonable to me.  Do I have any other options?
=> Does my present plan make sense both from a technical as well as money
=> standpoint?
=> 
=> I notice there are mass market NAS devices out there, but they seem to
=> start at around $1000 (e.g., this Buffalo product:
=> http://www.newegg.com/Product/Product.asp?Item=N82E16822155306) and I
=> am not sure how well they handle drive failures.
=> 
=> Thanks in advance for your ideas, suggestions & comments.
=> 
=> -- 
=> 
=> Ed Goppelt
=> http://www.hallwatch.org
=> ___________________________________________________________________________
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=> 


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___________________________________________________________________________
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