OpenZFS on OS X

I do full weekly backups of my pools to tape. Its my understanding that checksumming is done on any read or write, so will this in effect scrub the pools? I'm wondering if there is any point is doing a scrub on top of this routine or if it would just reduce drive life for no benefit.

If you do full backups, it reads all data and would check all checksums as part of it. You could still run a scrub once a month or something

@lundman

wouldnt it depend on how the backup was done?

I mean.. if you are zfs sending and recieving.. zfs knows the delta.. it never reads all the data.. just reads the diff as its sending it? it knows the changes at the block level so only new blocks data get read and transmitted.

and if you are rsync'ing the data.. does it really read each canditate file in its entirety or is it just looking at the delta of the files last modified date, size etc.. ?

now I concur that during an initial backup and all files are transferred they would be checksumed during that backup.. no so sure on delta backups?

macz wrote:@lundman

wouldnt it depend on how the backup was done?

I mean.. if you are zfs sending and recieving.. zfs knows the delta.. it never reads all the data.. just reads the diff as its sending it? it knows the changes at the block level so only new blocks data get read and transmitted.

and if you are rsync'ing the data.. does it really read each canditate file in its entirety or is it just looking at the delta of the files last modified date, size etc.. ?

now I concur that during an initial backup and all files are transferred they would be checksumed during that backup.. no so sure on delta backups?

I was careful to indicate "full backup" meaning not deltas.

Well duh.. you did say tape.. ie not delta.. sorry.. have not seen a tape machine in ages and it didnt even register...

I stand corrected.. hehe

macz wrote:Well duh.. you did say tape.. ie not delta.. sorry.. have not seen a tape machine in ages and it didnt even register...

I stand corrected.. hehe

No problem. LTO6 is the cheapest format per TB so its my tool of choice.