Re: PATCH: Raw device IO for 2.1.131
Dominik Kubla (dominik.kubla@uni-mainz.de)
Mon, 21 Dec 1998 18:23:47 +0100
On Thu, Dec 17, 1998 at 11:15:09AM -0500, Stefan Monnier wrote:
> >>>>> "Stephen" == Stephen Williams <steve@icarus.com> writes:
> > And what about the case the Oracle guy pointed out where they share a SCSI
> > disk between two hosts? Can that be made to work under Linux?
>
> It was an interesting case indeed, but I'm not sure about some of the details.
> It seems he presented several different cases all merged into one. Mostly
> two situations:
> - take-over in case of failure (only one machine ever accesses the drive at
> the same time). The only requirement here seems to be that hosts need
> some way to make sure that the disk data is consistent, so it's pretty much
> the same requirement as the single-host case.
> - parallel access from two hosts. I'm not quite sure why you'd want to do
> that. It seems to me that the only reason would be performance, but it
> seems that the disk and/or the SCSI bus would be the limiting factor rather
> than the host, so why have two hosts ?
>
> What am I missing ?
On the hardware side: Multi-channel RAID-Arrays, Fibrechannel, you name it.
On the economical side: It's way to expensive to have one of to database
servers sit idle most of the time. You want them both to be productive.
As always: just because you don't see it does not mean it does not exist...
Dominik Kubla
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