Re: [Hampshire] Drobo

> RAID 5 combines N drives (N>2) to provide (N-1)/N total capacity plus
> a parity disk. Any one drive fails it can be rebuilt from the others.

RAID-5 works well for the sort of size of array you're going to get in a
domestic situation.

I'm informed (by people who tend to know...) that it can cause issues with
very large arrays - the amount of work you need to do to rebuild the array
after a failure can push one or more of the remaining drives into failure.
And during failure, RAID-5 has no redundancy...

> Unless you want hardware RAID support any modern motherboard with enough
> SATA ports will do. Hardware RAID is expensive and often need propriatory
> support tools. Software RAID is built into the Linux kernel and the
> software overhead is rarely noticeable. Ignore the marketingspeak phoney
> RAID added to some mother boards, just count the total numer of ports.

I look after two customer machines that have a proprietary SCSI RAID array
(contrary to my advice when they bought them). One of the disks has
recently failed. Because of the hardware chosen, we're quite constrained
as to what we can replace it with - so the cost of a new disk is pretty
close to the residual value of this 5-year-old server.

Software RAID in Linux is a doddle.

> Don't know of a NAS distro. Basic RAID support should be in all of them
> these days.

I played with OpenFiler for a while. It shows plenty of promise - but a
number of its supposed features simply don't work (hotswapping, for
example, is very flakey). But the real reason to avoid it is that it's
based on rPath linux - so it's difficult to produce a slight variant of
their images without an awful lot of work...

It is my intention to port the OpenFiler app back to a RHEL-style build.
But that's not going to happen any time soon.

> Definitely feasible. Like all such projects however it won't save you
> money as soon as you put any sort of hourly rate on your time, it's
> marginal on hardware costs in any case. On the other hand it's probably
> an excellent learning/personal development project.

Indeed. I think everyone should build something like this, just to see how
easy RAID is under Linux. Just don't go spending serious money on that :-)

Vic.