Handbook obsolescence scan: "The vinum Volume Manager"

[Warren Block]

On Tue, 25 Jun 2013, Frank Leonhardt wrote:

> Couldn't agree more! In fact the whole disk mirroring thing still 
> confuses me, as there are too many options and no guide for choosing 
> between them. As far as I understand it, gmirror is the way to go in 
> most cases because you end up with two identical drives, either of 
> which can be salvaged from the wreckage after a crash, stuck in to 
> another PC and booted. ZFS is the solution if you want to spread lots 
> of data across lots of drives.

ZFS can do mirrors, too, and almost everything else.  Its weakness now 
is that it is relatively memory hungry.  So I would advise this:

gmirror(8) for data safety on machines with relatively limited memory.
graid(8) for software BIOS RAID.
ZFS for mirrors or more typical RAID arrays on machines with 4G of 
memory or more.

> Actually, in practical terms, I don't see why ZFS is better than pairs 
> (or threes) of gmirrored drives mounted on to one file system in the 
> traditional way. Perhaps I just don't get it, or perhaps I'm just too 
> traditional to give up on the idea that it's good to know which drive 
> a particular file is on.

It's RAID, so you get more space than mirrors, and possibly better 
performance for some things.  ZFS RAID-Z1 (and -Z2, -Z3) have a lower 
vacuum coefficient than RAID-5.  There are lots of nifty features, like 
being able to add storage without reformatting.

There are other options, but I suspect the three above cover most of the 
needs and are what we should be suggesting to new users in the Handbook.