Welcome back to the channel, and in this video
we're going to talk about disk selection for NAS. Because a common question is, "should I use
Enterprise disks or NAS specific disk for my NAS or Network Attached Storage". I run multiple
Synology NAS's and I've used them for about eight years now. Back then when I started I used
Western Digital Red disks, but I stopped using WD. I look for alternatives and there were a few
choices that stood out, but the thing that isn't clear specifically, is the choice of using
either Enterprise or using the NAS specific disks. Especially if enterprise are actually
cheaper for storage density, and this is true of Seagate disk right now, and it actually
has been for a while. I'm going to share why I moved away from Western Digital also because
it was important for me when choosing the disks I would use going forward. Going back to around
2005 I was at the time impressed with WDs disk storage density development and reliability but
three major things happen that made me decide to drop them. Firstly WD started to drop behind in
terms of density and capacity, and at the time Seagate was starting to make great strides in
terms of the disk capacity. This challenge could have been one of the reasons why WD made some of
the decisions that I'm going to come to. Secondly, going back some years I have been actually a huge
Seagate fan but they also went through a phase when I wasn't so impressed with their reliability, and
that's when I'd move away to WD. But now Seagate seemed to be doing a much better job in terms
of disk reliability and quality than they had be previously. As well as leading the way in terms
of capacity, and price to capacity ratios. But the real kicker for me was what happened with WD
and their use of SMR drives or Shingled Magnetic recording technology on their NAS Drives. And
ultimately this was the deciding factor for me. To give you some background there are a number of
technologies that disk manufacturers have used to increase data density. Since around the mid-2000s
this has been done primarily using something called PMR or perpendicular magnetic recording, and
this is also known as CMR or conventional magnetic recording. This technology simply places disk
tracks next to each other on the disk platters and writing the magnetic polarity into the
recording layer perpendicular to the write head. The innovation for increased capacity here
was really just increasing platter counts in the disk and also increasing areal density by making
these tracks and write heads smaller. But this was running into limiting factors around how small
these tracks could really be. One way to overcome this, was to use something called Shingled Magnetic
Recording, and with this approach the tracks partially overlap and this means that the size of
the right head and the granularity of the writing doesn't need to be so small. So this is fine but
it means that as you write data you're actually partially overwriting data on neighboring tracks
and you need to go and rewrite that data on those tracks that may have been overwritten. So this does
have an impact to sustain and write performance, if you want to write one Megabyte of data you may
need to rewrite several other Megabytes on those neighboring tracks to retain data consistency
and stability. This could have a particularly bad impact on very large writes especially things
like large RAID rebuilds. If your writes are fairly small and not continuous then this doesn't have
a serious impact, so it's a good technology for smaller writes and lower frequencies to reduce
cost. You can mitigate the limitations of SMR by using larger disk caches, now as data is written to
disk the write performance impact can be offset by writing to the larger cache which is fast and the
disk can then catch up from the cache. However if you're performing a lot of large writes then the
cache will fill and then you'll have delays on I/O to the disk as it performs these rewrites and
you get lower performance. And this is why these types of disks are less suitable for NAS use cases
where large files are being written often. But the use of SMR wasn't the reason I stopped using WD
specifically, I could have just stopped using those disks. The reason was that WD went to great
lengths to actively hide this from customers. Not only was it not documented but if you went looking
and asking the right questions you couldn't easily find out which disk had CMR and which had SMR. They
basically went to significant effort to hide what they were doing, presumably so they could keep up
with the price to capacity of their competitors. I originally used CMR Western Digital Red six
Terabyte disks at the time in my Synology DS2415 plus NAS but they replaced these disks with SMR
versions quietly and the only way I can identify which was which was by looking at the cache size.
The CMR drives had the part numbered WD60WFRX and this has 64 MB of cache and the SMR drives
were WD60EFAX and they had 256 Mb. So on face value the larger cache makes them look like better
drives. But that cache was there to mitigate the limitations of SMR write performance. Eventually,
and it really did take too long, WD were called out on this very publicly and they got a great deal
of customer backlash. This resulted in them keeping the WD Red range and using SMR, and then creating
a WD Red Plus range and using CMR technology. I actually tested one of these 'Plus' drives but due
to changes in firmware I wasn't even able to use the disk, it just wasn't recognized by my NAS. This
may have been fixed by now but having to send this disk back and all the previous problems, this is
when I decided that I was done with WD at this point. Now would I go back to WD? Yes, I would. But
they really need to do some work to catch up on their price to capacity and also there's definitely
some trust that needs to be rebuilt. And honestly my experience with the Western Digital Red range
has been really good, this six Terabyte disk for example has been running for nearly eight years.
But getting back to SMR discs more broadly, if you're using a NAS actively, especially if it's a
larger model using raid 5, SHRr or some other parity type, then I would avoid using SMR disks entirely.
So SMR aside, which disk to use. Let's look at the Seagate options and compare, because Seagate now
stands out as an excellent choice for NAS disks. So feature wise, there doesn't seem to be a lot
to separate the Iron Wolf Pro versus the Exos. There is reporting that both the Pro and Exos are
noisier drives, but the stated specifications at least, don't seem to bear that out. I also run two
12 bay NAS's in my office, with both pro disks and Exos, and I haven't noticed an issue in noise.
There is a slight increase in power consumption from the Iron Wolf to the Iron Wolf Pro and Exos,
but it isn't exceptional. The Exos also doesn't have a stated recommendation for Max drives per
enclosure, and this is most likely because it's an Enterprise Drive and designed to be placed in
very large enclosures with large numbers of disks. This "Bay Count" number actually comes from how the
drives detect and manage vibration, they can adjust their speed slightly so that they don't get into
a harmonic resonance with other drives in the same enclosure, which can cause vibrational wear. The Pro
disk is able to do this for any reasonable home or SMB enclosure, but 12 Bay enclosures like the
DS2419 may not be ideal for the Iron Wolf. Though my Synology 12 bay NAS has run six Terabyte Western
Digital Reds for many years, which have a similar limitation, and I haven't had any problems. And in
fact many of those now have lasted six or seven years. The fact the enclosure has dampening
mounts on the drive bay slightly helps with reducing vibrations passing through the chassis.
So now we've established where each product sits feature wise, let's review how these compare from
a cost perspective. And I looked at costs in the UK using scan.co.uk and in the US using Newegg,
and there's a similar theme in both locations. And I've also looked at other retailers as well and
see similar results. First of all, we see that the Iron Wolf range does not cater to the larger disk
size. So if you're looking for greater density you may be limited to either the Pro or Exos ranges.
Secondly, we see that it varies by range and in fact may vary over time periods where the best
price per Terabyte is. Typically, what you will see though, is the smaller form factor drives will drop
in price towards a floor and not maintain cost per Terabyte parity. This is partly as there's
a baseline cost to platform manufacturing, QA shipping and distribution etc. But also these
disks will get less manufacturing capacity over time, and will likely only be selling to those that
are looking for a like-like replacement. So smaller capacity drives typically carry a premium. We also
see that the higher density drives start out with a large premium and then as volume and yield
increases, they will drop in price. So the best cost price per Terabyte often sits in the middle, to the
middle upper of the range. It is worth considering however that there is a cost associated with the
slot in the NAS itself. So all NAS's, regardless of size, they have a certain number of bays. So
filling them with the largest possible drives give the best capacity to price for the NAS system
itself. So if a larger disk has a cost per Terabyte in a similar order to the smaller disk, it may
still be effectively cheaper to use that larger disk and maximize on NAS capacity. Okay let's
focus on the Pro disk versus the Exos disks. Here we see that despite having a general feature
advantage of the Pro disks, the Exos drives are actually cheaper per Terabyte across nearly the
entire range. The reasons for this may be many, and they may change over time. But this can include
economies of scale from manufacturing quantity, simpler or cheaper distribution, due to volume, and
margins or excess in stock capacity at a given time. If they have a lot of these drives sitting
on the shelf, they may be willing to sell them at a reduced price to get them moving. And finally,
the important consideration is compatibility. Talking specifically about the Synology lineup,
but this applies to others, they publish a list of supported drive models. Just because a drive isn't
on the list doesn't mean it won't work, but rather that it hasn't been tested and validated by the
vendor. This also means that new drives are more likely to be missing from the list as it takes
some time to resource and perform that testing. So for example at time of creating this video, the
exos 7e2 7e8 and the X10, X12, X14 and X16 drive ranges are supported, but nothing above 14 Terabytes
is actually on the list. For either the DS2415 Plus or the DS2422 which I use. However, I run x18 18
Terabyte drives in my Synology 2415 just fine and that NAS is nearly eight years old. You may need to
be running a decent release of the NAS OS, however that is possible. So conclusions, as it stands
today there doesn't seem to be a good reason not to run Exos disks versus either the IronWolf or the IronWolf Pro disk. The performance, warranty, scale and cost are all strongly in favor of
Exos. And there seems to be limited downside, the one thing I would be aware of is that comparative
pricing on these drives could change in the future. It is recommended, though it's not required to
run the same disk type in your NAS to prevent performance related issues. If you start your NAS
out with Exos disks, and you plan to grow its capacity over time, it is possible at some later
date that you need to pay a premium for these disks. However having been monitoring this for some
time that price has not been swinging between the IronWolf pro and the Exos, so this doesn't appear
to be a concern at least in the immediate future. So personally, I will continue using Exos disks
for the time being. So a big thank you for watching this to the end, and please drop a like if this
was interesting or helpful. Also I would love you to subscribe if the content is useful and you
want more of it in the future. Please also do give me your comments below if you have a perspective
or like alternate drive options. I would also be interested on your take on what happened with
WD's SMR drives, or if they manage to keep that quiet enough that you were not aware. And as
always, thank you and I will see you in the next....
