[maemo-developers] [maemo-developers] Re: Span filesystem across both SD cards?

[From: Jon Smirl]

On 2/3/07, Neil MacLeod <gmane at nmacleod.com> wrote:
> Jon Smirl wrote:
> > On 2/1/07, Jon Smirl <jonsmirl at gmail.com> wrote:
> > Your own time isn't free, I'd just buy a 2GB card instead spending
> > five or six hours trying to merge two 512MB ones.
> >
>
> I'm not sure the size of the cards really matters though - you can find yourself short of sufficient space on any individual card whether it is 512Mb or 8GB, yet across both cards you may have the space to store the file.
>
> I'd actually like to span across two 8GB cards giving a unified 16GB filesystem (or perhaps keep 1GB for swap and OS, and the remaining 15GB unified for media file storage). Even with 8GB cards I could find myself with insufficient room to squeeze in one more file on either card! :)

Using dm/lvm to merge the devices into a single large device means
that the cards are paired and can't be used individually anymore. If
you take one out and put it in a reader, you won't be able to read it.

The usb storage feature of the Nokia would also have to be modified to
export the merged drive instead of the individual sd devices. It
should be easy to point USB storage at a different device name.

You could also improve the read/write speed of the system by combining
the models into a raid0 array. That is probably easier than dm/lvm.
But for raid0 to be efficient the devices need to be identical. The
raid0 driver is a small module that can be built into the kernel, it
will stripe the file system across both devices without any
redundancy.

-- 
Jon Smirl
jonsmirl at gmail.com