"snapshot" RAID

[Tom Metro]

Dan Ritter wrote:
> ...I decided to experiment with *not* putting a RAID mirror on this
> machine. There is a second disk installed, but I keep it spun down
> with hdparm. Once a day an rsnapshot is taken and stored on sdb2.

This seems like a good solution for a portable machine where battery 
life matters.

I originally purchased a second identical drive for my primary laptop 
with plans to run RAID1, but due to battery, noise, and heat 
considerations, I decided against it.

The snapshot approach gets you enough redundancy, such that you can 
rescue the system, even when you're on the road and away from your 
backup storage, while not costing you power and noise constantly.

How about sharing the code you use to implement your backups?

I wouldn't expect rsnapshot to be used in this scenario. I gather your 
intention isn't to create an identical mirror on the second disk, but an 
archive of snapshots.

"Back In Time" - a GUI wrapper for rsync - could probably be substituted 
for rsnapshot. It has the ability to call out to a script at various 
points, so you could have it run the necessary hdparm commands 
before/after backup.

Though if the drives are identical in size, I think I'd be more likely 
to make snapshots to the primary drive, and periodically mirror the 
entire thing to the second drive.


> (sdb1 is a copy of the boot partition, tested and then never mounted.)

But that needs to be re-mirrored after each kernel update, no?

How often do you test it, and what are the steps you use to force the 
boot from the second drive? A BIOS setting? A mere GRUB menu option 
won't necessarily provide a true test, as that will still load GRUB from 
the primary drive's MBR.

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/