[openbeosstorage] Re: DiskDevice API v2.1
- From: "Ingo Weinhold" <bonefish@xxxxxxxxxxxxxxx>
- To: openbeosstorage@xxxxxxxxxxxxx
- Date: Wed, 09 Apr 2003 23:48:38 +0200 CEST
"Axel Dörfler" <axeld@xxxxxxxxxxxxxxxx> wrote:
> "Ingo Weinhold" <bonefish@xxxxxxxxxxxxxxx> wrote:
> > > A file wouldn't work - for example, in case of a sudden system
> > > death,
> > > you would still need to be able to load that data. And a file or
> > > any
> > > data on that partition might have been cut in half at that
> > > moment.
> > > You wouldn't be able to load the boot loader, nor to extract the
> > > data
> > > about how the partition structure currently looks.
> > I think, it should be possible to ensure, that at no point in time,
> > the
> > meta data are not available as a contiguous chunk. E.g. if the data
> > have to be moved (due to moving the partition or resizing it), I
> > would
> > first establish the data in the new place, then change the pointer
> > from
> > the old to the new location, and then do whatever else needs to be
> > done
> > (logging to the new location from that time on).
>
> If it's the boot partition, there are some more issues, like the
> bootloader, and the whole file system at this point.
> But in some point your right, since even with a spare partition, the
> boot loader would have to be able to locate drivers from that
> partition, and thus needs a basic understanding of the data in that
> partition.
I think it's even more complicated. Since the boot partition may be
unreadable, because the repartitioning had been interrupted, the
bootloader won't be able to read anything from it. So, all drivers/code
required to at least get the partition into a accessable state must be
on the spare partition (or whereever the meta data reside) so that the
boot loader can load it.
> Hm, perhaps we can make it a requirement only for the RAID case, but
> it's more work for sure (and might need more file system functions).
You mean, make the spare partition a requirement for RAID? When booting
from a partition on a RAID disk, I'm quite sure, we won't get around
having a partition on a non-RAID disk on which the RAID support code
resides.
> We'll see.
> I will first have a look how the file system API should look like to
> support all of this functionality, then it'll probably be clearer.
OK.
> > BTW, the same problem occures, when you have a meta partition and
> > move
> > it.
>
> Yes, and that's why the meta partition isn't intended to move ever.
> It
> would rather be recreated at a new location (say, another disk), than
> moved.
> I don't exactly see the need to move that partition around, though.
> It
> should always be located at the end or beginning of a disk.
Wasn't there a certain OS, that requires being installed on the first
primary partition?
CU, Ingo
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