I understand that the Drobo has an idiotic mechanism that intentionally throttles performance when you are at 95% capacity. This is fairly stupid, since I want to fill my drive to capacity and then use it as READ-ONLY and while I may be moving some content off and replacing it with other content every great once in awhile, it will not be “added to indefinitely”. Just filled to capacity and then read from (streaming to other devices).
Fairly ridiculous that this isn’t taken into account with Drobo’s “calculator”, since on a regular Drobo packed with 2tb drives, that reduces (needlessly) your storage by another 300gb. Not for any practical purpose other than “well, YOU might not be stupid enough to just keep dumping data on here forever, but OTHER people might”.
Anyway, via Firewire 800, I was getting
- Up to about 50% full, I got 30MB/s.
- After the Drobo reached 50% full, I was getting around 20MB/s.
- At 66% full, I’m getting 10.8MB/s
So, why is the performance degrading so horribly, already?
If I’m only getting 10.8MB/s at 66% full, how miserable is the slow-down at 80% or 90% or 95%?
Can I expect read-access to be this terrible? Does the throttling at 95% only apply to writing or is it reading, too? (And if it’s reading as well, WHY? I’m not ADDING data to it – I’m just READING from it and there’s no point in throttling that, even for the sake of an “idiot light” function).
I know this isn’t true RAID and that RAID can see certain performance degradation itself in certain circumstances, but those circumstances are not with 4x2tb drives at 50% capacity.
At these speeds, the Drobo boarders on becoming useless. I have 1.7tb still free (well, 1.4tb when you account for the 95% “idiot light” factor) and while the first 3.7tb took about 21 hours to copy over, I’m looking at another 40 hours to do 1.4tb. Assuming the speed doesn’t get worse (which it will – it’s now at 10.4MB/s).
The drives should not be overheating and there are no other significant concerns in the deployment environment. Using 2tb WD *EARS drives that Drobo uses and advises via FW800 on OSX via a machine that is not otherwise being touched and initially performed at 30MB/s with this Drobo 21 hours ago.