5D as a black box: two basic questions

Hello all,

Have been combing the site and forums and don’t see a clear answer to either of these questions, so I’m hoping a kind and clever soul will chime in here.

  1. I understand how the system can be single drive fault tolerant with 3 drives and still increase performance, whereas with 2 drives you have to pretty much write copies of your files to each of the two (and therefore experience speeds pretty close to “1x” drive speed"). Here is the question. If you start with two drives and and the third after you have begun filling your Drobo, is the 5D going to re-arrange everything internally or will files written before the 3rd drive always read out at “1x”?

  2. My 5D now has a Samsung 840 mSATA installed in the accelerator bay. WHICH applications can access this and how? I can see how write performance to the accelerator may be poor since it will mirror that to the spinning disks (or does it??) but how does it decide what lives on the mSATA? The accelerator bay seems to be the least documented part of this beast.

Thanks, have an excellent day/evening!

hi, welcome and heres a bit of info from my side meanwhile:

for 1)
if you have a drobo with 3 drives, you can have single (or dual) drive redundancy.
(dual helps protect you against 2 drive failures, but the more protection you have, the less free space you get to use)

if it is you, using your drobo, then i wouldnt worry too much about the speeds, because it’s still rather fast.
what i learned from docchris initially (if i understood correctly), for my original 4-slot drobos, was as follows:

  • put 2 drives in (drobo 4slot has only single drive protection)
  • put 3rd only when running low on space
  • put 4th only when running low on space

thats what i did and it worked fine for me even up to now…
in your case if you have 5 slots, and if you want 2 drives protected,
then you could put in 3 drives (= 1 drive’s space worth of usable space)
then put in 4th when needed
then put in 5th when needed.

the only benefit i can see to putting in extra drives into free slots if you have spare drives, is that it could help in the case of you having an unfortunate period of drive failures, in which case maybe the 2nd and 3rd drives fail, but can then re-protect the data set, using the 4th and 5th drives, back to dual protection again.

if you are going to have multiple users/connections using the drobo, (especially at the same time), then that can slow things down, as each user gets a slice of access, but you might be able to improve things a bit using faster drives up to a point.

for 2)
im not sure, but as far as i understood it, it only improved read speeds, though might not be noticable until you access the same data at least the 2nd time round.
Smart data aware tiering etc is hopefully not just a buzz-word, but even i couldnt figure out exectly how it works, and its probably a closely guarded secret (possibly listed within the patent specs but am not sure) :slight_smile: