[zfs-discuss] Offline vdev replace or remove via offline BPR ? (Feature request)

Christ Schlacta aarcane at aarcane.org
Sat May 5 02:38:38 EDT 2012

I know that "Block Pointer Rewrite" is a major hassle and a prerequisite 
for such features as online vdev replacement or removal and data 
reduplication..  This is kinda sucky, 'cause it's a lot of work, and the 
people involved kinda have to do it over from scratch.  Meanwhile, I'm 
repeatedly forced to wonder:  If I'm willing to do without my data for a 
handful of days, could "offline block pointer rewrite" be accomplished 
feasibly?  IE: import -N, vdev replace/remove, or "redup", etc. then 
export and reimport the pool and have the changes be in effect?  I would 
love to have such a feature made available.  I'd be willing to help with 
any of the lower level repetitive or interface tasks, but I've got no 
experience in the kernel or filesystem stuff.

The only feature that I'd ask be added above the basic is that it should 
be "somewhat" interruptible, IE: it should always keep ZFS consistent, 
or at least be able to make it consistent again if interrupted on 
purpose or accident quickly.  a 5 days long redup process obviously may 
need to be re-interrupted to gather some data, then resumed, etc..

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