Been finding some good deals on 2.5 disks lately, but have never bought one before. Have a couple of 3.5 disks on the other hand in my Unraid server. Wondering how much it matters wether I get a 2.5 or not? What form factor do you prefer/usually go for?
You’ll usually want 3.5" on anything that isn’t a laptop for the price and higher max speed
And theoretical reliability. Stuff breaks down quicker at smaller sizes says my lizard brain
Smaller stuff has smaller mass and therefore can be more reliable.
There were portable mp3 players with mechanical hard drives that were reliable despite extreme abuse.
Smaller stuff has to be more complex to get to the lower mass, which is usually what causes the biggest issues. The hdds in those ipods had some extra stuff to make them more reliable, but even then, move them too quickly and they show it.
Except the mp3 players from Archos, which gave up after setting up. Twice.
I think 3.5" are usually priced better per tb than 2.5" drives and performance is usually better too. So unless you feel like burning money for an inferior solution, are have some space constraints that doesn’t allow 3.5" drives, I wouldn’t go with 2.5" drives. They’re more energy efficient though, but you’d need a fuckton of drives for that to make a worthwhile difference in your power bill.
The key here is “better performance at similar price points”. There are absolutely amazing 2.5 drives made for server applications, but they cost so much money you’re better off getting SSD these days.
Speaking of which, you should consider SSD.
Man, I remember when Zip Disks were a big deal and a GB was a lot of storage.
Ssd for boot but not cost effective for nas. Nor do I trust their longevity.
SSD longevity seems to be better than HDDs overall. The limiting factor is how many write cycles the SSD can handle, but in most cases the write endurance is so high that it’s unreachable by most home/NAS systems.
SSDs are however really bad for cold storage, as they will lose the charge stored in their cells if left unpowered too long. When the SSD is powered it will automatically refresh the cells in the background to ensure they don’t lose their charge.
Probably best to go with something in the 3.5" line, unless you’re going enterprise 2.5" (which are entirely different birds than consumer drives)
Whatever you get for your NAS, make sure it’s CMR and not SMR. SMR drives do not perform well in NAS arrays.
Many years ago I for some low cost 2.5" Barracuda for my servers only to find out years after I bought them that they were SMR and that may have been a contributing factor to them not being as fast as I expected.
TLDR: Read the datasheet
Whatever you get for your NAS, make sure it’s CMR and not SMR. SMR drives do not perform well in NAS arrays.
I just want to follow this up and stress how important it is. This isn’t “oh, it kinda sucks but you can tolerate it” territory. It’s actually unusable after a certain point. I inherited a Synology NAS at my current job which is used for backup storage, and my job was to figure out why it wasn’t working anymore. After investigation, I found out the guy before me populated it with cheapo SMR drives, and after a certain point they just become literally unusable due to the ripple effect of rewrites inherent to shingled drives. I tried to format the array of five 6TB drives and start fresh, and it told me it would take 30 days to run whatever “optimization” process it performs after a format. After leaving it running for several days, I realized it wasn’t joking. During this period, I was getting around 1MB/s throughput to the system.
Do not buy SMR drives for any parity RAID usage, ever. It is fundamentally incompatible with how parity RAID (RAID5/6, ZFS RAID-Z, etc) writes across multiple disks. SMR should only be used for write-once situations, and ideally only for cold storage.
3.5" are cheaper, go up to higher capacities (2.5" maxes out at only 5TB IIRC), and are easier to find cheap in used/refurb formats.
I wouldn’t use 2.5" unless you absolutely had to for some reason.
The 2.5" drives are significantly more power efficient, often by a factor of 10. They also tend to be less noisy and produce less heat.
So in a small form factor NAS that isn’t under heavy load, 2.5” drives are usually the better option.
It looks like about 2-3W with 2.5" vs 6-8W with 3.5"
So 3.5" drives are going to be more efficient, since you can get one that’s 4x the capacity (20TB vs 5TB) for only a little over double the power usage.
Less noise is definitely a bonus if your NAS sits next to your workstation or something though.
It is true that if you need a lot of space at some point 3.5" are going to be more efficient per GB, but usually people don’t need hundreds of terabyte storage in a home NAS.
For normal applications in a home NAS that mostly sits idle, 2.5" drives run at about 1W and most are design to be able to be powered by normal USB, meaning 2.5W max.
3.5" drives on the other hand are usually designed for datacenter use, where power efficiency is a low priority and they usually take 5-10W in normal operation and and easily 15W when spinning up.
2.5" disks are SMR, you don’t want that in a raid.
For the record, so are a lot of 3.5s. Always read up on your drives before buying.
Here you can check if a drive is CMR or SMR:
https://nascompares.com/answer/list-of-wd-cmr-and-smr-hard-drives-hdd/
the 3.5" barracuda disks are SMR. the barracuda pro disks are all CMR. https://www.seagate.com/products/cmr-smr-list/
SMR is a relatively new disk format technology that makes drives cheaper but writes slower, which can be noticeably bad in a NAS, especially if you are using a write-intensive RAID type. Most disk manufacturers will have drives meant for NAS like WD Red or Seagate Ironwolf, and they are almost all CMR and not SMR.
WD reds I believe are smr, wd red pros are cmr, or at least that was a thing for a while that WD did silently.
Basically the write head writes over part of the magnetic track below the current track, reducing the physical size of each data and increasing how much data can be stored on one side of a disk.They’re bad for random writes because the drive would need to rewrite data in the track below it as well.
