[CentOS] ZFS on Linux in production?

[Chuck Munro]

On 10/25/2013, 05:00 , centos-request at centos.org wrote:
> We are a CentOS shop, and have the lucky, fortunate problem of having
> ever-increasing amounts of data to manage. EXT3/4 becomes tough to
> manage when you start climbing, especially when you have to upgrade, so
> we're contemplating switching to ZFS.
>
> As of last spring, it appears that ZFS On Linuxhttp://zfsonlinux.org/
> calls itself production ready despite a version number of 0.6.2, and
> being acknowledged as unstable on 32 bit systems.
>
> However, given the need to do backups, zfs send sounds like a godsend
> over rsync which is running into scaling problems of its own. (EG:
> Nightly backups are being threatened by the possibility of taking over
> 24 hours per backup)
>
> Was wondering if anybody here could weigh in with real-life experience?
> Performance/scalability?
>
> -Ben

FWIW, I manage a small IT shop with a redundant pair of ZFS file servers 
running the  zfsonlinux.org  package on 64-bit ScientificLinux-6 
platforms.  CentOS-6 would work just as well.  Installing it with yum 
couldn't be simpler, but configuring it takes a bit of reading and 
experimentation.  I reserved a bit more than 1GByte of RAM for each 
TByte of disk.

One machine (20 useable TBytes in raid-z3) is the SMB server for all of 
the clients, and the other machine (identically configured) sits in the 
background acting as a hot spare.  Users tell me that performance is 
quite good.

After about 2 months of testing, there have been no problems whatsoever, 
although I'll admit the servers do not operate under much stress.  There 
is a cron job on each machine that does a scrub every Sunday.

The old ext4 primary file servers have been shut down and the ZFS boxes 
put into production, although one of the old ext4 servers will remain 
rsync'd to the new machines for a few more months (just in case).

The new servers have the zfsonlinux repositories configured for manual 
updates, but the two machines tend to be left alone unless there are 
important security updates or new features I need.

To keep the two servers in sync I use 'lsyncd' which is essentially a 
front-end for rsync that cuts down thrashing and overhead dramatically 
by excluding the full filesystem scan and using inotify to figure out 
what to sync.  This allows almost-real-time syncing of the backup 
machine.  (BTW, you need to crank the resources for inotify waaaaay up 
for large filesystems with a couple million files.)

So far, so good.  I still have a *lot* to learn about ZFS and its 
feature set, but for now it's doing the job very nicely.  I don't miss 
the long ext4 periodic fsck's one bit  :-)

YMMV, of course,
Chuck