maximumpc.com JUN 2019 MAXIMUMPC 17
Alex Campbell
OPEN SOURCE
Do You Need Traditional
RAID in Your Server?
DATA HOARDERS REJOICE: If you’re building a home server, you’re not
constrained to using traditional JBOD, RAID, or RAID-Z. SnapRAID and
MergerFS offer JBOD-like storage advantages with the data security you’d
expect from RAID 5. For most home users, the performance is more than
enough. And you’ll be able to use heterogeneous drives to boot.
To keep costs down when building a home server,
i t ’s a g o o d i d e a t o m a k e u s e o f a n y e x i s t i n g h a r d w a r e
you have. But one of those hardware requirements
may warrant thought: the hard drives.
The first thought you might have is to create a
traditional RAID or RAID-Z array. Those solutions
are fine, but if you think about it, a traditional RAID
array has a few requirements that aren’t great.
First off, RAID arrays require all the hard
drives to be up and spinning for any read or write
operation. This alone has consequences, one of
which is energy use. Sure, a few watts may not
sound like much, but when drives are spinning
24/7, it can be like leaving several 60W light bulbs
on all the time, and this can add up.
Heat becomes a problem as well. I ran my
home server with five drives in a RAID 5 array for
a long time, with the server in my home office.
Sacramento summers can be hot, and having five
spinning drives up all the time made the room
unbearable. Along with heat comes noise. Keeping
drives cool means running fans all the time.
When I decided to rebuild my server in October, I
looked for another method that would maximize my
storage while maintaining a level of data security
(through RAID 5-like parity). I stumbled across
SnapRAID and MergerFS, which is what I run now.
SnapRAID with MergerFS is a little like a JBOD
(just a bunch of disks) array in disguise. MergerFS
operates on top of a drive’s filesystems, and allows
you to use your drives as a single logical drive.
SnapRAID handles parity and backup operations,
so you can restore data if a drive fails. You’ll have
to do this through snapshotting, however.
From a cost perspective, this is great. With
typical RAID arrays, it is recommended to use
identical drives. With SnapRAID and MergerFS, I
could take my 5TB drives and add a
couple unused 4TB and 1TB drives.
SnapRAID also only has to
spin up one drive at a time for file
access. This can save life on your
drive motors, keep energy use
down, and reduce heat. SnapRAID
attempts to fill one drive at a time,
too. This means that unused drives
largely stay at rest until needed.
The bad thing about this, of course,
is that one drive may be taking the
brunt of access requests.
One of the downsides of using
SnapRAID/MergerFS is that reads
aren’t as fast as traditional RAID.
But if you’re using the machine as a
server, there’s a good chance that
your gigabit network is saturated
by the reads from a single driveanyway. If you’re accessing your
server over the Internet, your
upload speeds dictate your read
performance as well. Basically,
outside of having a 10Gb network,
SnapRAID/MergerFS perform just
fine for most home networks.
If you’re looking to build a
server, take a look at SnapRAID
(free software under GPLv3) and
MergerFS (open source under
the MIT-like ISC license). If you
decide to try it, there’s a great
guide from LinuxServer.io (https://
blog.linuxserver.io/2017/06/24/
the-perfect-media-server-2017/).Alex Campbell is a Linux geek
who enjoys learning about
computer security.Storage mounts on a server; note the MergerFS volume and parity drive.