The Drobo 5D should be nice piece of kit. It combines multiple disk drives into a single giant drive, which can cope with a single drive failure (you just pop it out and replace it with a new one).In reality it has cost me a fortune in additional drives, and has proven extremely unreliable. I purchased a Drobo 5D with five 3TB WD NAS drives. This is what happened:1) The USB cable supplied with the Drobo 5D didn't work. Drobo support blamed my USB 3 card and recommended a list of expensive cards. Fixed with a new USB cable.2) The Drobo has a “feature” whereby it cripples itself if it goes over 95% full and the transfer speed plummets to about 2MB/sec. The problem I had is that I was using an encrypted partition (Truecrypt) that can't reduce in size! I couldn't copy the data off the Drobo because it was so slow so the only solution was to upgrade my 3TB drives to 4TB drives.3) I bought two 4TB drives (Seagate ST4000VN000) from two different sources and put them in. This gave me the space but file access speed varied enormously, some files were 60MB/sec and some were still 2MB/sec. Drobo support said my new drives were faulty and recommended some nice expensive ones to buy. I pointed out that the chances of two drives from different suppliers being faulty in exactly the same way was unlikely, and asked if there were any compatibility issues with these drives. I'm still waiting for an answer to that several months on. The Seagate drives work fine on their own in the main computer.4) I bought three 4TB drives (WD WD40EFRX) and they worked fine for a few months. Then one day a red light appears indicating a drive has died. I reboot the computer and the Drobo recovers, but takes 2 days for it to rebuild. I buy another 4TB WD drive to replace the one which produced the red light as I no longer trust it.5) I ask Drobo support if they think the problem was with the drive or the Drobo. They ask for diagnostics but when I send them the file produced by the Drobo they say they it has missing information and ask me to reboot the Drobo. I do that and it no longer comes up. It's now a very expensive doorstop.6) Drobo support say that it will take 10 days to replace it as it has to be shipped to Germany, and I have to pay the postage.So to summarise, so far I have bought a Drobo 5D and 11 large and expensive multi-terabyte disk drives - and have zero Drobo storage.I do not recommend this product.