[prev in list] [next in list] [prev in thread] [next in thread] 

List:       linux-lvm
Subject:    Re: [linux-lvm] label sector and non 512 byte sectors
From:       Stuart D Gathman <stuart () bmsi ! com>
Date:       2013-01-03 19:13:20
Message-ID: alpine.LRH.2.02.1301031410370.28451 () bmsred ! bmsi ! com
[Download RAW message or body]

On Jan 3, Alasdair G Kergon transmitted in part:

> On Wed, Dec 26, 2012 at 09:59:00AM -0500, Phillip Susi wrote:
>> The man page for pvcreate states that the label goes in the second
>> sector.  That means it SHOULD be at an offset of 4096 bytes when using
>> 4096 byte sectors, but apparently it is still at an offset of 512 bytes.
>>  Bug?
>
> We define a sector at 512 bytes. Always.
>
> Some documentation could be improved to make that clearer.

And current storage devices always define a logical sector as 512 bytes,
and the firmware takes care of the R/M/W (with caching) needed for
partial or unaligned writes.

The physical sector size is important when *aligning* LVM segments, filesystem
blocks, RAID clusters, etc.

_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
[prev in list] [next in list] [prev in thread] [next in thread]