Re: [Hampshire] Drobo

Alan Pope wrote:
> Ok, there's one thing to note about making a DIY drobo, you can
> probably achieve pretty much everything the drobo does, except one
> thing (easily). The ability to hot swap drives of random sizes and it
> all just work. Whilst you can easily make a machine that can auto
> expand an array as the user slaps more storage in the box, one key
> thing the drobo does well is shrinking again. I can yank a disk out
> (or it fail) and the system automagically rebuilds a _resilient_
> solution on the remaining disks. If another disk goes pop and there's
> enough space left to store all my data then that's viable too. Again
> the rebuild/reorg happens and you're magically left with a resilient
> system, ready for more disks.
>
> It's this "magic sauce" that nobody else does.
>

The (very expensive) HP SANs we use do that, but in a production
environment (where data is being written and read at speed) it is
actually a disadvantage. If a disk dies, or is removed, the system
spends so much effort shuffling data around that the external I/O
performance suffers horribly. I would much rather take the small
performance hit of recalculating lost data on the fly, and waiting for a
replacement disk to be inserted, than for it to spend several hours
moving data unnecessarily.

Simon