Which drive to replace?


I have a Drobo containing, from top to bottom,: 500GB, 500GB, 500GB, 1TB.

  • The three 500GB drives came from dismantled Western Digital My Book enclosures.

  • The 1TB drive came from dismantling some kind of Maxtor external enclosure.

So my question is this: which of the three 500GB drives do I replace. Is there any way of telling which is the oldest/noisiest/most likely to fail? My main concern at the moment is increasing capacity and reducing the noise, as my Drobo has been blowing like a hair-dryer in the recent warm weather.

Finally, could someone try to estimate how long the rebuild process will take when replacing one of the 500GB drives with a 2TB drive? My Drobo currently has 726.78GB of Used Space and 639.88GB of Free Space.

Thanks in advance,


there is no way to tell those things while the drive sare in drobo.

you could turn drobo off, pull out the 500gb drives and use a pc or mac to query their SMART information to find out their total number of power on hours to figure out which is oldest/most used. but frankly its hardly worth it.

i’d just pull a random one

i would guess 12-18 hours for your rebuild (it will be significantly longer if you continue to use drobo while it is rebuilding

Thanks for the very quick reply. Just one more question…

I know this has been discussed endlessly on these boards, but I’d value your opinion - given that I can quite easily not use my computer for the 24 hours a rebuild might take, is it best to replace the drive with my computer (iMac) on or off?



For fastest rebuild time, unmount Drobo and disconnect it from your computer. That will ensure no other access will slow down the rebuild/relayout.