On Fri, 19 Oct 2007, Doug Ledford wrote:
On Fri, 2007-10-19 at 11:46 -0400, John Stoffel wrote:
"Justin" == Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> writes:
Justin> On Fri, 19 Oct 2007, John Stoffel wrote:
So,
Is it time to start thinking about deprecating the old 0.9, 1.0 and
1.1 formats to just standardize on the 1.2 format? What are the
issues surrounding this?
1.0, 1.1, and 1.2 are the same format, just in different positions on
the disk. Of the three, the 1.1 format is the safest to use since it
won't allow you to accidentally have some sort of metadata between the
beginning of the disk and the raid superblock (such as an lvm2
superblock), and hence whenever the raid array isn't up, you won't be
able to accidentally mount the lvm2 volumes, filesystem, etc. (In worse
case situations, I've seen lvm2 find a superblock on one RAID1 array
member when the RAID1 array was down, the system came up, you used the
system, the two copies of the raid array were made drastically
inconsistent, then at the next reboot, the situation that prevented the
RAID1 from starting was resolved, and it never know it failed to start
last time, and the two inconsistent members we put back into a clean
array). So, deprecating any of these is not really helpful. And you
need to keep the old 0.90 format around for back compatibility with
thousands of existing raid arrays.
Agree, what is the benefit in deprecating them? Is there that much old
code or?
It's certainly easy enough to change mdadm to default to the 1.2
format and to require a --force switch to allow use of the older
formats.
I keep seeing that we support these old formats, and it's never been
clear to me why we have four different ones available? Why can't we
start defining the canonical format for Linux RAID metadata?
Thanks,
John
john@xxxxxxxxxxx
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Justin> I hope 00.90.03 is not deprecated, LILO cannot boot off of
Justin> anything else!
Are you sure? I find that GRUB is much easier to use and setup than
LILO these days. But hey, just dropping down to support 00.09.03 and
1.2 formats would be fine too. Let's just lessen the confusion if at
all possible.
John
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--
Doug Ledford <dledford@xxxxxxxxxx>
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http://people.redhat.com/dledford
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