software raid on removable drives for backups

[Jason Joines]

Net Llama! wrote:
> On Wed, 2 Feb 2005, Jason Joines wrote:
>>	My boss wanted to be able to retrieve data up to twelve weeks old even
>>if one drive of a set died.  We were using RAID 5 with 4 drives.  We had
>>several drive failures over the years they were in use but no data loss
>>thanks to the RAID.
> 
> i have to ask.  what kind of drives are you using, how many died, and over
> how many years?  With just 4 drives, any more than a single drive failure
> over ~3 years suggests a bigger issue.
> 


	It wasn't just four drives.  There were 6 sets of 4 drives and 1 set of 
3 drives.  The 4 drive sets were for weekly and monthly backups and the 
3 drive set was used for daily backups.  These were exported via NFS and 
backups were done to them via xfsdump, dump, tar, etc., depending on the 
situation.  Every week, the four drive sets were rotated out but the 3 
drive set was left in all the time.  So there were 27 drives total and 
at least 3 failed over the three year period, seems like there were more 
but I can't remember for sure.  They were all 80 GB Maxtor D540X drives. 
  So the schedule went like this.

sat	week1	full
sun-fri	daily	decremental
sat	week2	full
sun-fri	daily	decremental
sat	week3	full
sun-fri	daily	decremental
sat	month1	full
sun-fri	daily	decremental
sat	week1	full
sun-fri	daily	decremental
sat	week2	full
sun-fri	daily	decremental
sat	week3	full
sun-fri	daily	decremental
sat	month2	full
sat	week1	full
sun-fri	daily	decremental
sat	week2	full
sun-fri	daily	decremental
sat	week3	full
sun-fri	daily	decremental
sat	month3	full
REPEAT

Jason
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