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[Discuss] NAS: lots of bays vs. lots of boxes

Tom Metro <tmetro+blu at> writes:

> Derek Atkins wrote:
>> I plan to build a freenas box.  I can get a 24-bay 4U case and build
>> into it for about the same price as a synology...
> That's fine if you need lots of drives to achieve your capacity
> requirements in the bear term. If you do, the DIY approach is very
> appealing, as you can accommodate a lot of spindles for a small
> incremental cost.
> I've gone down that path as a thought experiment. Having the ability to
> handle lots of drives gives you the comforting feeling that you can
> always expand capacity easily by adding another drive.
> But the reality is that you only need to be able to expand capacity at a
> rate faster than your needs are growing, and for lots of use cases the
> rate at which the industry increases density per dive outpaces this. If
> not, then add a couple more drive bays, and repeat the math until your
> overall array shows a predicted capacity increase from drive density
> than your predicted need.
> A box with 24-bays is going to be rather expensive if your short term
> needs are for only 4 or 6 bays. Unless a high percentage of those are
> for "near line" backup storage, you need to support those bays with more
> RAM, more SATA ports, faster CPU, more Ethernet ports, etc.

The 24-bay NORCO box is under $400.

At the start I'd be using at least 10 bays (6 large spinning drives in
Raid-Z2, and 4 SSDs in RAID-10), moving to 12 pretty shortly thereafter
(expanding the RAID-10).  I suspect I'll fill another 6 bays (another
Raid-Z2) as soon as my wife and I start to move our audio and video
collection over.

> And then you've got an expensive box with a ton of storage and a single
> point of failure.

I already have a single point of failure; this is just moving it to a
different single point of failure.

> I'm more interested in clever ways of using multiple, cheap, commodity
> NAS boxes, Google-style. For example, for the same cost as that $600+
> (diskless) DIY NAS I linked to, I can get 4 of the QNAP 2-bay boxes and
> maybe combine them with something like MooseFS. You get redundancy where
> some number of the boxes can go down, and it still keeps working, and
> you can expand capacity by adding more boxes (if drive density increases
> don't keep pace).

This might be an interesting exercise if I can get enough total storage.
On the other hand I've found that my failures are usually related to
power, which is yet another single point of failure, and one that I
can't get redundantly in my house.  :)

>  -Tom


       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL:    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available

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