software raid on removable drives for backups

[Jason Joines]

Mike Reinehr wrote:
> With my _very_ limited knowledge of  RAID this may be a case of "fools rush 
> in ...", but  I've been spending time this winter setting up new servers with 
> software RAID and what you describe sounds feasible to me. Using mdadm and 
> writing a RAID superblock to each drive you should easily be able to manually 
> assemble (run) your pre-defined RAID devices. Once assembled, you just would 
> mount the assembled RAID device, e.g. /dev/md0 read-only, to access the data. 
> When finished, unmount and stop the RAID device and unplug the drives. (I 
> have no experience with hotplugging SCSI drives -- caveat emptor.)
> 
> I would suggest reading up on mdadm & see what you think. If you already have 
> the drives and your sure that they hotplug safely, what have you got to 
> loose?
> 
> cmr
> 
> 
> On Tuesday 01 February 2005 03:30 pm, Jason Joines wrote:
>>    I'd like to use sets of big removable drives as backup media.
>>Ideally, a 3 disk RAID-5 set would be built and a weekly backup written
>>to it.  Then, another 3 disk set would be stuck in .....  Only problem
>>is I would need to be able to non-destructively reinsert the first set
>>to get data off of it if a restore was needed.  Can software raid do this?
>>
>>    For the past three years I'd been using an Adaptec 2400A ATA raid
>>card to do this.  Actually 2 cards.  One card had four 80 Gb drives in
>>RAID 5 and daily backups were written to it.  The other card had six
>>sets of four 80 Gb that were swapped in and out for weekly and monthly
>>backups.  It was much faster and cheaper than tape.  We recently needed
>>to upgrade our capacity so an Adaptec 2810SA card was purchased and the
>>same thing attempted with big SATA drives.  After many problems and
>>destroyed backups Adaptec just told me the card couldn't be used this
>>way and it shouldn't have worked on the 2400A either.
>>
>>Jason Joines
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> 

	I guess we'll give it a try.  We don't need hotplugging (although it 
would be nice) we've just been powering off, inserting the new set, and 
powering back on.  I just hoped to hear for sure that it works before 
trying it.  My last weekly backup was just fried and I hadn't copied it 
anywhere (takes a long time to copy 400 GB and hard to find places to 
put it).  I sure don't want to lose another.

Jason
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