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?
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.
the 3.5" barracuda disks are SMR. the barracuda pro disks are all CMR. https://www.seagate.com/products/cmr-smr-list/
SMR ? What is that
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.
i have had SMR drives slow to about 2MB/s with sustained sequential writes. “noticeably bad” really undersells how terrible they are.
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.
Indeed, it’s worth explicitly checking every drive you buy if you are using it in a NAS.
Important note; some WD Reds are still SMR. You have to check which specific type.
Shingled Magnetic Recording
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.