[rhelv6-beta-list] Can RHEL6 installer align the disk partition with 4k-sector or raid stripe size?

[Nico Kadel-Garcia]

On Sun, Jun 6, 2010 at 12:50 PM,  <caiqian at redhat.com> wrote:
>
>> Can RHEL6 installer align the disk partition with 4k-sector or raid
>> stripe size?
> Yes, this should be possible, and been tested in certain degree in-house. Have you seen any problem?
>
> C.

I assume that the original poster mant "4k block size". 4k sectors....
doesn't make much sense.

So far as I can tell, this only works with hard drives which are
detected as 4K block size. According to my preliminary tests, it does
*NOT* work with VMware, Xen, or KVM disk images. This is an important
feature for certain attached storage devices, such as NetApps, which
behave very badly if the partitions of virtual disk images are not 4K
aligned. It should, ideally, be a simple setting for disk
configuration in Anaconda and especially in a virtual machine setup
tool, but even fdisk mishandles this: at least up through RHEL 5.

You see, you can set the block size with fdisk inside a '%pre'
statement. But if you don't have a partition set, fdisk automagically
reverts the block size to 512 for you. This means that in order to
preserve the block size information for Anaconda's disk configuration
tools, which have *no* options to select specific sectors to start or
end partitions, or to do this 4K block size, you have to set aside a
partition that anaconda will not touch and that will preserve th e4096
block size setting. That's.... fairly awkward to allocate and recover
later.

I've also found no way to tell Anaconda "I've built the partitions for
you in %pre: use *THESE* partitions for *THOSE* mount points, and
don't try to repartiton them." If someone knows a way, I'd love to
hear it.