backing up with parity data

[shecky]

now that i am building my network storage box, i have decided that ultimately the way i am going to run a backup routine is a couple of sets of hard drives that i will copy data to in an external enclosure, remove from the enclosure and store safely offsite and rotate as needed. after much research, i am convinced that this is the best mix of price, convenience and reliability so long as they are regularly rotated and re-written with current backup data.

i have also been reading about including parity data on the backups to aid in restoration if some sectors go bad or other non-total catastrophes - not in terms of a RAID array, but extra data on each of my single disk backups. can anyone enlighten me on this a bit under OS X? specifically, any software you use to do this.

 

[orangemacapple]

rather than shuffling disks around, why not just backup to an offsite computer or use idisk?

automate backups and never worry about them again. sneakernet seems to be kinda obsolete.

 

[CanadaRAM]

rather than shuffling disks around, why not just backup to an offsite computer or use idisk?

automate backups and never worry about them again. sneakernet seems to be kinda obsolete.

Because online offsite storage space is limited, and transmission on the intertubes is sometimes too slow to be practical.

Shecky, I have customers who are doing what you are planning, docking enclosure with drives in trays that they alternate to offsite storage. It's the only way to go if you are backing up 100 GB + data sets.

Personally, I wouldn't bother with adding any kind of parity storage, just make sure that your backup program does a verify read-after-write.

 

[shecky]

rather than shuffling disks around, why not just backup to an offsite computer or use idisk?

beacuse backing up a TB of data to an online disk not only sounds like it would take forever, and be expensive, but i have no reason to do so when i feel i have a solution that works for me. i would consider backing up a few GB's of "need it this second no matter what wherever i am in the planet" current working data, but for archival stuff no way.

Because online offsite storage space is limited, and transmission on the intertubes is sometimes too slow to be practical.

what he said

Shecky, I have customers who are doing what you are planning, docking enclosure with drives in trays that they alternate to offsite storage. It's the only way to go if you are backing up 100 GB + data sets.

i agree - i have really looked at this and considered everything from tape drives to high-end DVD+R and i think that backing up to rotating HD's just makes the most sense when you factor in everything.

Personally, I wouldn't bother with adding any kind of parity storage, just make sure that your backup program does a verify read-after-write.

i thought the idea of parity data was less about the initial data transfer screwing up (which a verify would catch) and more about something happening down the line with bad sectors/drive bumped around/whatever? or will a verify do the same thing? me = confused

 

[CanadaRAM]

A verify doesn't do anything for damage to the drive post-facto. It's just a check that what you wrote came across perfectly, and a warning flag if it didn't.

Given that it is rotating data and you will always have a second generation backup, I wouldn't be too concerned. Calculating and saving Parity data will take longer (would slow the transfer down) and consume some degree of space.

Be interested to know however what software are out there to do it.

Of course if you have a 2 bay enclosure you could always just mirror the backups, for the cost of 2x the number of drive mechanisms.