Beginners questions

[Justin Sherrill]

On Sun, Dec 1, 2013 at 11:44 AM, Cassandra von Ahrcanburg <
proudmouse at tlink.de> wrote:

> On Fri, 29 Nov 2013 15:26:51 -0500
> Nikolai Lifanov <lifanov at mail.lifanov.com> wrote:
>
> > You will have a much better experience adding disks to HAMMER than
> > ZFS. HAMMER relies on hardware raid for redundancy, and you can just
> > add "hammer volume-add" new disks and it will concatenate them.
> > With ZFS, you have to add disks one leg at a time. So, with a
> > triple-parity raid10 with 2 legs (6 disks), you will have to add 3
> > disks at a time. To a raidz2 with 8 disks, you will need to add 8 at
> > a time... You get the picture.
>
> I wasn't going to use a hardware RAID at all. A friend of mine works
> for a company that builds and installs servers and workstations in all
> sorts of firms. They often use RAID controllers and judging by the
> amount of failures they encounter (and I don't even think he told me
> all the stories there are to tell), I don't see any real advantages in
> hardware RAID. Quite often I get to hear stories about a disc dying and
> the RAID controller refusing to accept a replacement and rebuild the
> RAID, although the drive is of same make and model. I'll give software
> RAID a chance.
>

I'd argue it may be a symptom of pseudo-hardware RAID, of which there's a
lot - hardware devices that don't present a unified volume image to the
operating system, and depend on a software driver to accomplish what they
do.



> When using FreeBSD this can be setup with ZFS alone. AFAIK HAMMER will
> need the LVM for the volumes. Can I still grow the RAID as I need it
> (one disc at a time)?
>

Well, you can hammer-add all day long - but this is not a RAID; you lose a
disk, that data is gone unless you have it streaming to another Hammer
volume.  People have used vinum on DragonFly for software RAID, which may
work as an option.

You'll have to do some contortions to get what you want; Hammer and ZFS are
different beasts, but what you want to do is expressed in terms of ZFS
features, which is why there isn't a straight answer.
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