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

[Nico Kadel-Garcia]

On Tue, Jun 8, 2010 at 3:01 AM, Justin Clift <justin at salasaga.org> wrote:
> On 06/08/2010 09:37 AM, Nico Kadel-Garcia wrote:
> <snip>
>>
>> This is thoughtful, but it's relevant only to physical media, not
>> virtual images. Until virtualization "disks" are configurable as "4096
>> byte block devices", the emulated disks have a behavioral issue that
>> the guest OS's cannot see.
>
> As a data point, one of the test setups we have here exports luns over the
> network with 4k sector sizes.  These are mounted on host servers, and
> assigned directly to guests for use as storage.

Those are LUN's, which require considerably more resources on the
virtualization servers. Feasible, but expensive.

I've been working with NFS mounted images. Those are cheaper, but
don't appear to "fdisk" as 4096 byte block devices.

> From the guests' perspective these are physical disks with real 4k sector
> sizes.  If the guests utilities only support 512 byte sectors, then strange
> errors and bad things happen due to the mismatch. (incorrect usage of space,
> no ability to boot, etc).
>
> Using (very recent) guests that support 4k sectors (through using recent
> grub and parted), and the guests install and operate fine.
>
> On the plus side, using 4k sector sizes for guests over the network like
> this seems to have a very positive effect on the backend disk IO
> performance.

I'd love to do so. Even aligning the partitions on 4096 byte
boundaries helps tremendously with NetApps providing the virtual disk
images over NFS, but I'm going bugfutz trying to get this into
kickstart tools. I'm hoping that RHEL 6's kickstart tools will make it
easier.

>
> Regards and best wishes,
>
> Justin Clift
>
> --
> Salasaga  -  Open Source eLearning IDE
>              http://www.salasaga.org
>