off-site backup plan

[Eric Shubert]

Alex Dean wrote:
> 
> On Oct 21, 2009, at 12:11 PM, Matt Graham wrote:
> 
>> From: "Dorian Monroe" <dorian.monroe at cox.net>
>>> I don't understand how anyone could consider RAID a "backup" plan.
>>> 'Cause it's not.
> 
> You may be misunderstanding my architecture.  The system in question 
> exists to make backups of other systems.  I'm not using RAID as a backup 
> plan.  I'm using rdiff-backup as a backup plan.  :)  RAID is to provide 
> redundancy on the backup server.
> 
>>
>> RAID-1 with a hot spare, where you periodically deactivate the spare,
>> then slap a new spare in, then take the old spare and put it
>> somewhere else, could be used as a backup.  I believe they were
>> referring to that method, since Alex said he was thinking about
>> doing that in the message that started this thread.
> 
> Indeed, that was my original plan.
> 
> I'm still reading around trying to figure out if I can get hot-plugging 
> SATA or eSATA.  If I can get confident that that will work, I will 
> probably go that route.  Otherwise, USB will be the fallback plan.
> 
> I'm having a hard time researching disk controllers (especially those 
> integrated w/ motherboards).  Is an eSATA port really different from a 
> SATA port?  Some info I've found states they are distinct, and you need 
> an eSATA port to do hot-plugging.  Other people have reported getting 
> hot-plug with a normal SATA port, but I'm not sure whether that's 
> because they're correct, or whether they're just lucky so far and will 
> eventually fry their disks or panic their kernel.  It's all quite 
> confusing for a lowly programmer who doesn't do much hardware kludgery.
> 
>>
>> FWIW, the every-week connect+rsync of a USB2 drive and ~120G of data
>> approach that I'm using takes about 5 minutes wall-clock and 30
>> seconds of plugging/unplugging and typing 2 commands.
> 
> Hot-plug in USB is a much more well-known proposition.  Decent fallback 
> plan if the SATA stuff finally gets the best of me.
> 
> thanks,
> alex
> 

.) I don't know about hot-plugging drives. Since you're talking about a 
backup server though, what's the big deal about hot swapping? Just shut 
the thing down and swap the drives. What's the advantage to leaving it on?

.) The hot spare in a soft raid array has no data on it. It's only used 
when another drive in the array fails. You can however set up 3 drives 
in a raid-1 array, remove 1 and 2 will still be active, then add another 
drive to replace the removed one. In any case I think you'll need to do 
a command (mdadm /dev/md? --add /dev/sd??) to add the new 
drive/partition back into the array.

.) I like the rsync/USB solution the best. rsync doesn't really take 
that long, even with USB (slow) connected drives. I have a backup server 
running raid-1 on USB drives. The only real problem I had was that the 
raid array tried to start before the USB drives were completely active. 
Added a "sleep 10" statement in the init script and it works fine. If 
you really need more speed, use eSATA with external drives instead of 
USB. Yes, eSATA and SATA are different.

-- 
-Eric 'shubes'