Re: cgd + zfs

[Pouya Tafti <pouya+lists.netbsd%nohup.io@localhost>]

> 

[pouya+lists.netbsd%nohup.io@localhost]
> >> I'm now thinking, would it make sense to do the layering the other
> >> way around, i.e. have cgd on top of a zvol?  I wonder if there would
> >> be any resilience (and possibly performance) advantage to having zfs
> >> directly access the hard drives (which, being old and bought off
> >> ebay, I don't quite trust) rather than go through cgd.

[brad%anduin.eldar.org@localhost]
> > To be honest about it, I don't remember if I tested in that direction.
> > It would be simple enough to try.  You just might have the same problem
> > with missing IOCTLs that keeps swapping from working.

[gdt%lexort.com@localhost]
> If you put cgd on zvol, then what filesystem are you putting in the cgd?
> Another zfs pool? ufs2?   To me, zfs on cgd makes more sense, because
> then you actually get zfs, and can have raidz2 or whatever, but all
> media is encrypted.

Thanks to everyone who has responded.  I agree putting zfs on cgd would seem cleaner.  Potential reasons to do it the other way around could be:

1) Not being familiar with the implementation details of either cgd or zfs, I'm under the (perhaps wrong) impression that zfs may be more resilient to hardware errors and partial failures if it talks to the hardware more directly, and not through cgd.

2) I imagine you could zfs send encrypted volumes for remote backups.  But there may be better options available for encrypted backups that I'm not aware of.