Small Form Factor (SFF) / 2.5" disks seem to have become more popular than LFF disks now due to them being preferable over LFF disks in many scenarios (lower power consumption, higher density, etc). However, LFF disks still seem to feature in major vendor's offerings (take the recently released Gen9 series of HP servers as an example).
Looking at the pricing of the disks, in most of the lower (sub-500GB) capacities, there seems to be little price difference these days. That begs the question, why are they still popular enough for vendors to feel it's worth investing in supporting them in their latest products? Is it purely because the LFF form factor disks are available into higher capacities than SFF disks, or are there other reasons why they are still popular?
Underlying this is the fact I'm trying to understand what objective justification there is for spec'ing out a modern server with LFF cages/disks over SSF. What scenario/requirements might mean LFF would be the preferred choice? Would you only really do this if you needed large, multi-terabyte disks at a sensible cost, or are there other reasons?
Best Answer
Use 2.5" disks for enterprise SAS workloads and 3.5" for bulk and high-capacity storage.
You've answered your own question. Buy the right type of server for your anticipated workload. If you need high performance drives, optimize for that. If you need a lot of storage, then focus on that.
Small-form-factor (2.5") disks are available in the following capacities:
Large-form-factor (3.5") disks were/are available in
and
e.g. Buying a 600GB SAS 3.5" 15k RPM enterprise disk would be a mistake today, as would purchasing a 1TB SATA 2.5" 7.2k RPM drive. Both of those are well outside of the sweet spot and ideal application for their respective form factors.
A note about HP's ProLiant servers: Large-form-factor 3.5" disks are NOT featured prominently in the product line. You may see LFF disks in product photos and marketing material, but all of the product SKUs that you'll likely see in distribution are going to be SFF. Only a couple of low-end models of the DL380 Gen9, for instance, are spec'd with 3.5" disks.