this post was submitted on 03 Jun 2024
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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?

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[–] tomten 20 points 5 months ago (3 children)

2.5" disks are SMR, you don't want that in a raid.

[–] [email protected] 23 points 5 months ago (1 children)

For the record, so are a lot of 3.5s. Always read up on your drives before buying.

[–] [email protected] 10 points 5 months ago (2 children)
[–] [email protected] 2 points 5 months ago

Awsome resource. You win the Internet today.

[–] [email protected] 1 points 5 months ago* (last edited 5 months ago) (1 children)

Thanks. But sad that this list is needed.

[–] [email protected] 1 points 5 months ago (1 children)

It's actually a big improvement for drives that don't need a constant transfer rate. Fewer platters and/or higher data density. It's helped push capacity up for 2.5" drives. I use a couple for cold backups and I appreciate the larger capacity in a small format.

[–] [email protected] 12 points 5 months ago

the 3.5" barracuda disks are SMR. the barracuda pro disks are all CMR. https://www.seagate.com/products/cmr-smr-list/

[–] Krafting 9 points 5 months ago (2 children)
[–] [email protected] 15 points 5 months ago (3 children)

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.

[–] [email protected] 7 points 5 months ago

i have had SMR drives slow to about 2MB/s with sustained sequential writes. "noticeably bad" really undersells how terrible they are.

[–] [email protected] 6 points 5 months ago* (last edited 5 months ago) (1 children)

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.

[–] [email protected] 1 points 5 months ago

Indeed, it’s worth explicitly checking every drive you buy if you are using it in a NAS.

[–] [email protected] 1 points 5 months ago

Important note; some WD Reds are still SMR. You have to check which specific type.

[–] [email protected] 9 points 5 months ago

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.