Re: [patch] document flash/RAID dangers

[Pavel Machek]

Hi!

> The other thing about this thread is that the only RAID implementation
> that is being discussed here is the MD RAID stack.  There are a lot of
> RAID implementations that have the same issues:
> 
> - motherboard (aka "fake") RAID - In Linux this is typically mapped with
>   device mapper via dmraid; AFAIK there is not a tool to scrub (or even
>   monitor the status of and notify on failure) a Linux DM RAID setup.
> 
> - hardware RAID cards without battery backup - these have the exact same
>   issues because they cannot guarantee all writes complete, nor can they
>   keep track of incomplete writes across power failures
> 
> - hardware RAID cards _with_ battery backup but that don't periodically
>   test the battery and have a way to notify you of battery failure while
>   Linux is running
> 
> The issues being raised here are not specific to extX, MD RAID, or Linux
> at all; they are problems with non-"enterprise-class" RAID setups.
> There's a reason enterprise-class RAID costs a lot more money than the
> card you can pick up at Fry's.
> 
> There's no reason to document the design issues of general RAID
> implementations in the Linux kernel.

Even when we carry one of those misdesigned implementations in-tree?
(Note that fixed implementations do exist -- AIX? -- just add journal).

'I wont't tell you that this pony bites, because many ponies do bite'?

WTF? I thought we had higher moral standard than this.

							Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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