new fan, which airflow direction is correct? - please help

Hello everybody,

I have a short and simple, but important question: I want to change the fan on the back of my Drobo as the stock is much too loud. (I do this at my own risk, of course, and know that this voids any warranty.) I already opened the Drobo and removed the old fan. As I had to wait a few days until my new fan arrived, I now forgot which way the old one was inside. Therefore, I wanna ask: Is somebody here 100% sure which way the air direction is supposed to flow - should the fan blow hot air out or suck cold air in? (I guessed the first way, but I’m not sure anymore …) I would be VERY grateful if anybody could give me an answer. THANKS A MILLION in advance!!

I have drobo v2 and the fan on the back side sucks hot air out.

(I would prefer if fan would pump cool and filtered (dust free) air in instead.)

The air blows out from the back.

Hi Jennifer and Bytec - thanks for your very fast answer, very appreciated. This is the way I expected this. Bytec: Do you think that the other way round would have a better cooling effect or is your wish just because of the dust?

Greetings from Germany!

AFAIK over-pressuring (pump fresh air in) gives better cooling effect than under-pressuring (suck hot air out) and the dust factor is just a bonus.

I have replaced the front of my Drobo v2 with a 140mm fan.
Now it is totally silent, the drives are cooler and the original fan in Drobo works as a backup. Admittedly it is ugly, but I can live with it.

I probably got unlucky and got one of those noisy Drobos and my wife couldn’t stand it, despite being in the next room.

I am also curious about what fan you are placing in the Drobo. I have not made measurements, but it should be possible squeeze in a 120mm fan. That would really improve airflow.

STB: Interesting - I have chosen the Nexus Real Silent Fan 80mm with 1500rpm which I also don’t hear. Wonder which one keeps cooler, my Nexus or your fan (it fits into the Drobo?) which is bigger, but has less rpm. I would change to your one if you or somebody else could confirm that this is the better solution …

EDIT: Now that I’ve read your post again, it seems as if it does NOT fit into your drobo, but is on the outside. You did install it on the front where the lamps are? From where do you get the power?

drobo v2 fan specs:

Model : AD0912UB-A70GL
Kind : DC-Fan
Framesize : 92x92x25 mm
Flow : 56.62 CFM (~96.2 m3/h)
Noise : 39.4 dBA
Speed : ~3000 RPM

You must have some kind of ventilation that can give air flow not less than original fan. Otherwise I think you risk overheating your system.

Hi Bytec,

thanks for the note. As I compare the spec to my new fan (only 32,3 m3/h = 20,2 CFM), my fan surely is too powerless. Damn … Mabye I should really try a bigger 120mm? Nexus has one which still is very silent, but has 62,7 m3/h = 36,9 CFM. Still less than the original fan, but mabye okay to take the risk …?

Two Questions regardimng items in this thread, I don’t want to hijack, but now I’m curious.

  1. Bytec, where are you getting the fan information? from the Dashboard? I don’t use dashboard as I use linux, but also use the droboshare and the linux version doesn’t support the proprietary things needed to work over the network :frowning:

  2. Did you simply retrofit your second fan to the front of your drobo? do you have pics, installation process? Perhaps this would be a neat how-to, separate thread idea.

I get information from label on the fan and google search …

I have placed my fan in front of the Drobo. It is just standing on a piece of rubber foam because I didn’t want to drill holes in the front and void the warranty.
It got very low airflow but is absolutely silent.

Dimensions: 140 x 140 x 25mm

RPM: 600 +/- 10% RPM

Noise: 9 dBA

Airflow: 39 CFM, 66 m³/h

The internal fan in the Drobo does not seem to be working at all and the drives are very cool.

The power supply is from the inside of my computer. I have ordered an extension for the fan cable so I will soon be able to mount the side of the computer again. :slight_smile:

Just to let you all know: Considering the REAL significant power comparing my new 80mm Nexus fan to the stock one (I knew it was weaker, but didn’t knew the dimensions until I read the data sheets), I will go the safe route and change it to a more powerful one - even if that means that the Drobo gets a bit louder again. (Which will be still A LOT more quit than with the bad stock one.) Just to let you know so you don’t worry my Drobo could burn my house … :slight_smile:


I thought the posting was representing your fan speeds and thermal indications of the Drobo itself, not just the specs lol sorry. Thanks for the picture though. Cool hard drives are happy hard drives indeed.

I think you should consider buying a larger one. Measure and see if you can fit a 120mm fan there. That way you should be able to improve both airflow and sound. The original fan looks just too small in that large space.

Yeah, I will definitely look for this. 120mm could become a bit tricky though - it would fit inside of the drobo, but at the same time it doesn’t as the metal body of the Drobo makes the opening smaller at the end (a few millimeters on the left and the right) so that I probably won’t be able to place the back plate with a 120mm fan on it back. (If you understand what I mean - difficult to describe for me in English …) Anyway, I’ll find a solution. Thanks!