Does a full backup scrub a pool?

All your general support questions for OpenZFS on OS X.

Does a full backup scrub a pool?

Postby e8vww » Fri Feb 09, 2018 2:50 am

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.
e8vww
 
Posts: 51
Joined: Fri Nov 24, 2017 2:06 pm

Re: Does a full backup scrub a pool?

Postby lundman » Fri Feb 09, 2018 11:37 am

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
User avatar
lundman
 
Posts: 402
Joined: Thu Mar 06, 2014 2:05 pm
Location: Tokyo, Japan

Re: Does a full backup scrub a pool?

Postby macz » Sun Feb 18, 2018 6:33 pm

@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
 
Posts: 53
Joined: Wed Feb 03, 2016 4:54 am

Re: Does a full backup scrub a pool?

Postby e8vww » Tue Feb 20, 2018 4:23 am

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.
e8vww
 
Posts: 51
Joined: Fri Nov 24, 2017 2:06 pm

Re: Does a full backup scrub a pool?

Postby macz » Tue Feb 20, 2018 9:22 pm

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
 
Posts: 53
Joined: Wed Feb 03, 2016 4:54 am

Re: Does a full backup scrub a pool?

Postby e8vww » Tue Feb 27, 2018 11:54 am

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.
e8vww
 
Posts: 51
Joined: Fri Nov 24, 2017 2:06 pm


Return to General Help

Who is online

Users browsing this forum: No registered users and 3 guests

cron