Re: md (software) RAID missing in the installer for sparc
On Tue, 17 Apr 2007, Josip Rodin wrote:
I wasn't able to reproduce the working condition with a 3.5 GB root (/) md0
partition, or a 2 GB root md0. :( I've finally created a 256 MB /boot md0,
and a 5 GB root (/) md1 partition, and finally PROM found SILO.
Someone who knows PROM and/or SILO could explain which of those variables
causes the boot process to fail.
There are several factors involved.
1) The OBP does not understand raid, but it should be able to
cope with a simple mirror.
2) Older OBPs cannot see beyond either 1Gb or 2Gb into a partition
depending on version. If your installer puts anything needed for
the initial boot process beyond this point you will not be able
to boot. [ Affects Sparc32 ]
3) The first cylinder of the disk contains the partition information.
Most filesystems work around this by not actually using the first
cylinder, but Linux Raid does not understand this and it will
overwrite the tables. The solution is simple - just create a small
partition of one cylinder at cylinder zero and do not use it.
[ Affects Linux Raid and possibly oddball filesystems such as XFS
only when they start at cylinder zero ]
4) If the partition table on the disk was first written by an old
version of the Solaris format command the maximum useable size of
any partition will be either 1Gb or 2Gb depending on version.
Linux will probably not notice and allow you to create a larger
partition which will confuse the OBP even if the OBP does not have
the limitation in 2) above.
The workaround for this is to destroy cylinder zero by filling it
with zeros using dd and then use Linux fdisk to create a new BSD
table. [ Affects disks initially formatted with old utilities ]
You could have any combination of the above - best to avoid them all.
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