Question about drive selection - 5400 vs. 7200.

Hi All,

I have a 5N with a 64GB Crucial SSD accelerator installed. It has five 2TB WD Caviar Black hard drives (7200 RPM).

One of the drives bit the dust, so I am trying to figure out what to replace it with. Am looking at the Seagate NAS 4TB drive, but it’s only 5400 RPM.

I mainly use the Drobo as a backup for my photography (am semi-pro) and also as storage for my Plex streaming content (I use an iMac as my Plex server though, as I’d like to be able to transcode, if needed.)

Anyone have an opinion on if I’d be crippling my speed if I used a 5400 RPM drive to replace my 7200?

Thanks for the help!

  • Jon

I would recommend replacing with a 7200 RPM drive; using a slower drive will have performance implications.


I dont think it would make any differnece at all, especially in the 5N.

the drobo itself is considerably slower than even 5400 rpm disks - the limiting factor will always be the drobo, not the disks.

The 5400 RPM drive will run cooler… and as Docchris states, drive speed won’t make a difference in the 5N.

Drive speed does have an impact on performance, particularly the latency of an operation; in addition, many operations access multiple disks as a set, and the slowest disk will control the overall completion of the operation.


Heat, heat, heat. Avoid 7200 drives in the Drobo or any NAS.

hi i think while it could (from a general user perspective) seem to not make much difference when accessing some files or streaming a movie clip etc, certain operations, or internal operations, such as rebuilding, data scrubbing or space reclaiming etc Would gain from rpm speed overall, especially if all the drives are running at the same higher rpm level, to avoid the slowest one being the slowest point in the chain.

(of course, more rpm can lead to higher marketed costs of drives in some cases, or more heat / electricity usage depending on the model etc)

if someone is going to do lots of intensive work with their data, the speed gain could be more noticable with higher 7200 rpms, depending on the operations, though if you just want to use yoru drobo as basic storage or nothing very intensive, then you might not need the higher rpms. (for example i was able to do live audio capture from and to my gen1 drobo, or play some games and demos off it, using 5400 drives and it was fine for me and that was on an xp machine too. :)[hr]
btw just re-reading the top post,
if all the drives have been 7200 rpm so far (then you might as well try to get the replacement drive as 7200 as well) - in the sense that if the replacement is only 5400 then it could effectively be the weakest (or in this case, slowest) link in the chain, and could force most operations to only be able to run or complete at that slower speed.

so in your specific case, if all of your working drives are already 7200, i think you might as well try to get another one of the same if you can, especially if the speed of use you have been having has been fine for you, and also if the cost is the same as a 5400.

Heat is not a problem, and Drobo’s fans will provide any necessary cooling. 7200 RPM should always be used, and definitely in preference to 5400 RPM, for best performance.

Backblaze reported some data on drive temp/failure rate correlation, and basically showed there wasn’t any




Could not disagree more. the Drobo 5N is a slow unit, i cannot think of any circumstance in which you would be able to tell the slightest difference between the two drive speeds.

Latency - the network connection will be by far the slowest link

Rebuilds - the processor isn’t fast enough to even slightly tax a 5,400 rpm drive the 7,200 rpm drive wont make things any faster

and the rebuild point is ignoring the fact that modern 5,400 have almost as fast sustained speeds as 7,200 due to their increase density

in short - in most drobos, and especially in the 5n, don’t worry about drive speed.