- the Pegasus R6 in 6x 2TB HDD (12TB) unit can be had for as little as £1300 (several German suppliers on Ebay, for example, amongst others - within the EU so no additional import duties/VAT to be paid either). And if you take the drives the come with it, sell them (~£450 return), then upgrade to either 3TB or 4TB HDD's, you see even greater price per TB: eg.
1300-450 (sold 2TB drives) =£850. +690 (6x3TB WD Red's) =£1540 [for 18TB, thus =£85/TB!!]
1300-450 (sold 2TB drives) =£850. +900 (6x4TB Hitachi Deskstar 7K's) =£1750 [for 24TB, thus =£72/TB!!]
vs. your Drobo 5D you priced at £1450 for 15TB (5x 3TB WD Red's) & 256 Crucial mSATA = £97/TB.
It's obvious which works out more cost effective in shear capacity terms, when priced-up properly. And that's before we talk about performance terms...
- the R6 doesn't need the "SSD accelerator", as it works much faster than the Drobo 5D Thunderbolt, across raid levels (that's including even in raid 1/5/6, nevermind the speeds one gets out of it in raid 0).
- the R6 has a proper raid controller in it, making transfers sustainably faster and more reliable than the 5D's proprietary Beyond Raid system.
The only thing that may be of use to a few users, is being able to use different size drives and updating them in the future (and suffering the problems that go along with doing that in terms of performance loss); this is it's raison d'Ítre.
But really the R6 is more of a higher-end professional unit (not the top-end professional Thunderbolt units, but then they cost $8000+(!) from the likes of Sonnet et al -- making the Pegasus very reasonable when held in comparison) that gives better performance and better bang for buck when you add plenty of storage from the get-go - as opposed to adding it later on the 5D and having all the associated performance heartaches a high percentage of Drobo owners have always reported across Drobo models.
Examples from some professional photographers, on leaving Drobo storage behind:
+ countless more from 'informed' professional users.
It may be right for you for the HDD upgrade option, but the facts stand as they are. Pity, but there it is.