mark at gaiahost.coop
Fri Jul 1 19:27:53 GMT 2005
On Thu, Jun 30, 2005 at 04:34:13PM -0500, Dan Nelson wrote:
> In the last episode (Jun 30), Mark Bucciarelli said:
> > I don't see the big win in hardware raid.
> The three big plusses for hardware raid are: if you get one with
> battery-backed cache (strongly recommended), then the array can cache raid-5
> writes until it gets full stripes, and can hold off doing mirror writes if
> there are pending read requests.
Ah ... this is certainly a win for an io-bound system.
> Also, if your power goes out or the system spontaneously reboots, you won't
> have to rebuild parity or resync the mirrors (assuming battery-backed
We pay a lot of money to ensure the lights stay on and sacrifice small animals
to avoid spontaneous reboots.
> And finally, hardware raid cards will automatically rebuild onto a hot spare
I know I could do this with Linux software raid, not sure about gmirror.
> if available and you can swap out the dead drive and swap a new spare in
> without having to run a single command.
Another win. Thanks, your brought up some issues I hadn't thought of.
I expect hardware raid cards will go the way of modems and printers and
offload their processing to the main CPU. And I guess the choice partly
depends on whose software you trust more--free software from FreeBSD or
proprietary code written in a cathedral. You can probabaly guess my bias. ;)
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