Why should I use a NAS instead of a computer drive?

TrueNAS General
1

What is the fundamental difference between hard drive mechanisms that are made for NASs and those made for computers?

What would happen, if I equipped my NAS with computer drives to make an array?

2

Standard desktop computer drives can be the following:

  • They may use SMR technology. Shingled Magnetic Recording allows higher density writing at a cost of time needed to save other data, and later re-write it. SMR drives are not suitable for use with ZFS because of it’s COW, Copy On Write architecture. That COW competes with the SMR’s own Copy On Write causing ZFS to be much slower on SMR drives than standard drives.

  • Regular computer drives, especially laptop drives, park their heads more often than really needed. This can wear out the parking mechanism sooner that expected. As in 50,000 head parks in mere months of use. Some drives allow disabling that fast auto-park, or slowing it down.

  • Desktop drives make a time consuming effort to recover bad blocks. Including taking more than 1 minute. With that excessive time, ZFS has declared the drive dead, not just having a bad block that needs sparing out. NAS drives set the timeout to 7 seconds or less. This is called TLER, Time Limited Error Recovery by some disk manufacturers. Some desktop drives allow changing TLER.

  • Some NAS drives are designed to work with other NAS drives in the same enclosure. This is for vibration control which can cause other drives to fail early. Its not much of a concern, but some people use in-expensive disk enclosures which transmit the vibration to other drives. Some desktop drives can be set to slow down, thus cause less vibration.

  • Then their is heat… Many NAS drives are designed to work continuously for 3 to 5 years. Desktop drives may not survive that long.

As for what would happen if you used non-NAS drives for NAS purposes?

It varies and is less predictable. Thus, less reliable. But, many people do so quite successfully. Its a case if you care about your data, treat it well. (If your budget allows…)

One guy I knew got bit by the TLER. He had to keep re-syncing one of his RAID drives until I explained what could be happening. After using a NAS drive, no further problems.

4 Likes
3

That is a good question and here are some of the differences:

  1. A typical computer drive may be SMR.
  2. A NAS drive will allow multiple retries to read data before calling it a failed read operation. Video drives ignore failed data. And typical computer drives may try to read the data a few times but the generate a failure after a shorter attempt of recovery.
  3. Typical computer drives may sleep/spin down, not always desirable in a NAS. However NAS drive can typically spin down as well, but it is not the default setting.
  4. One other thing I can think of off the top of my head is vibration detection. NAS drives typically are expected to be in groups of HDDs and that causes harmonic vibrations which can affect the drives operations. Normal computer drive typically do not have this feature. To be honest, while I understand the science behind it, I’m not sure I’m a big believer in this as long as you properly mount the drives.

You can definitely install a non-NAS HDD and your system is apt to work perfectly fine and even last you a long time, but if the drive sleeps a lot and your system is somewhat active, it could mean a lot of spinning up operations which is very wearing on the drive, so if that feature can be disabled, I recommend you do that and verify it by observing the head load/unload cycles.

Hope this helps some.

2 Likes
4

Thanks very much for those awesome responses!

I have never been tempted to use drive mechanisms other than NAS drives in my NAS. It was merely a point of curiosity about the different modes of operation of the main classes of drives. Of those @Arwen and @joeschmuck have identified desktop, NAS and NVR drives. Are there others?

5

In my initial response I was only thinking spinning drives, but there is one drive type which is becoming very popular and I have an entire NAS using just this type of drive, NVMe. The price per TB is higher however the cooling requirements and power draw as significantly less, and they are silent.

These are the others I am aware of are: CMR/PMR (PMR is a type of CMR recording, added here to reduce any confusion), SMR, NVR. I don’t know of any other spinning rust drives (they are no longer iron oxide, they are generally made with cobalt-chromium-platinum (CoCrPt) or similar magnetic material on a glass platter).

So, CMR, SSD/NVMe is the preferred drive types for ZFS. I only use SMR drives as external USB Archive drives. Write once, read hopefully never as this is a deep backup and should there ever be a hurricane headed my way, I grab that drive and run. I am considering an external NVMe drive but I’m having a difficult time using one of my 4TB NVMe drives for this purpose due to cost.