Re: Got a call at 4am - RAID Gurus Please Read

[Javier J <javier () advancedmachines us>]

Hey guys, I am running it on freeBSD. (nas4free)

It's my understanding that when a resilver happens in a zpool, only the
data that has actually been written to the disks gets used, not the whole
array like traditional raid5 does, reading even empty blocks. I know I
should be using RAIDZ2 for this size array, but I have daily backups off of
this array and also this is a lab, not a production environment. In a
production environment I would use raidz2 or raidz3. The bottom line is
even just Raidz1 is way better than any RAID5 hardware/software solution I
have come across. 1 disk with ZFS can survive 1/8 of the disk becoming
destroyed apparently. ZFS itself has many protections against data
corruption. Also I have scheduled a zpool scrub to run twice a week (to
detect bitrot before it happens.)

Anyway. I have been using linux raid since it has been available and I ask
myself, why haven't I used ZFS seriously before now.

- J

On Thu, Dec 11, 2014 at 11:06 AM, Bacon Zombie <baconzombie () gmail com>
wrote:

> Are you running ZFS and RAIDZ on Linux or BSD?
> On 10 Dec 2014 23:21, "Javier J" <javier () advancedmachines us> wrote:
>
> > I'm just going to chime in here since I recently had to deal with bit-rot
> > affecting a 6TB linux raid5 setup using mdadm (6x 1TB disks)
> >
> > We couldn't rebuild because of 5 URE sectors on one of the other disks in
> > the array after a power / ups issue rebooted our storage box.
> >
> > We are now using ZFS RAIDZ and the question I ask myself is, why wasn't I
> > using ZFS years ago?
> >
> > +1 for ZFS and RAIDZ
> >
> >
> >
> > On Wed, Dec 10, 2014 at 8:40 AM, Rob Seastrom <rs () seastrom com> wrote:
> >
> > > The subject is drifting a bit but I'm going with the flow here:
> > >
> > > Seth Mos <seth.mos () dds nl> writes:
> > >
> > > > Raid10 is the only valid raid format these days. With the disks as big
> > > > as they get these days it's possible for silent corruption.
> > >
> > > How do you detect it?  A man with two watches is never sure what time it
> > > is.
> > >
> > > Unless you have a filesystem that detects and corrects silent
> > > corruption, you're still hosed, you just don't know it yet.  RAID10
> > > between the disks in and of itself doesn't help.
> > >
> > > > And with 4TB+ disks that is a real thing.  Raid 6 is ok, if you accept
> > > > rebuilds that take a week, literally. Although the rebuild rate on our
> > > > 11 disk raid 6 SSD array (2TB) is less then a day.
> > >
> > > I did a rebuild on a RAIDZ2 vdev recently (made out of 4tb WD reds).
> > > It took nowhere near a day let alone a week.  Theoretically takes 8-11
> > > hours if the vdev is completely full, proportionately less if it's
> > > not, and I was at about 2/3 in use.
> > >
> > > -r