[mythtv-users] DroboShare and HD Question

Simon Hobson linux at thehobsons.co.uk
Mon Feb 8 09:24:06 UTC 2010


John Drescher wrote:
>  > Personally, I don't understand the fascination with Drobo. It's a
>>  proprietary system, so you're stuck with what they want you to have.
>
>I do not either.

Ditto. When I read their list of plus points (dynamic reconfig, 
overcommit on space) I find my self thinking about how stuff is 
probably mixed up on the disks. Fine if everything keeps running, but 
if it all goes wrong then probably zero chance of recovering anything 
- without spending huge amount with a specialist recovery outfit (if 
they can do it).

>This will be no more reliable than the raid 5 you are
>coming from. To me its very unusual that 2 drives had a hardware
>failure at exactly the same time.

Actually that is a risk with disk arrays. You tend to buy a set of 
drives at one point - so they'll likely come from the same batch. 
Then you run them under near identical loads etc for identical 
running times. Statistically, there's a significant risk of related 
failures that are correlated in time - especially given the long 
rebuild times on some large arrays now.

I've personally experienced that, though fortunately I noticed 
recoverable error warnings in the logs before anything actually 
failed completely. I think we had to replace three or four drives in 
an array that (from memory) was probably no bigger than 4 drives 
(striped & mirrors for performance).

That's one of the reasons there's a lot of interest in multiple drive 
redundancy - especially in very large arrays where rebuild times can 
be a significant proportion of the MTBF, and so there is a 
significant risk of a second drive failure before a previous one has 
been fixed (even by automatically using a hot spare).

-- 
Simon Hobson

WANTED: "Software CD ROM Kit" for Canon CLBP 360-PS printer (Canon 
part no RH6-3612, or possibly RH6-3810, or RH6-3610 might do). I've a 
dead HD and need this CD so I can replace the disk and re-install the 
printer OS on it. If anyone knows where I might get hold of one I'd 
be grateful - requests to Canon drew a blank, it's been out of 
support for years.
Alternatively, if anyone has one of these and would let me image 
their hard disk ...

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.


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