* [linux-lvm] label sector and non 512 byte sectors
@ 2012-12-26 14:59 Phillip Susi
2013-01-03 18:02 ` Alasdair G Kergon
0 siblings, 1 reply; 3+ messages in thread
From: Phillip Susi @ 2012-12-26 14:59 UTC (permalink / raw)
To: LVM general discussion and development
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?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [linux-lvm] label sector and non 512 byte sectors
2012-12-26 14:59 [linux-lvm] label sector and non 512 byte sectors Phillip Susi
@ 2013-01-03 18:02 ` Alasdair G Kergon
2013-01-03 19:13 ` Stuart D Gathman
0 siblings, 1 reply; 3+ messages in thread
From: Alasdair G Kergon @ 2013-01-03 18:02 UTC (permalink / raw)
To: LVM general discussion and development
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.
Alasdair
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [linux-lvm] label sector and non 512 byte sectors
2013-01-03 18:02 ` Alasdair G Kergon
@ 2013-01-03 19:13 ` Stuart D Gathman
0 siblings, 0 replies; 3+ messages in thread
From: Stuart D Gathman @ 2013-01-03 19:13 UTC (permalink / raw)
To: LVM general discussion and development
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.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-12-26 14:59 [linux-lvm] label sector and non 512 byte sectors Phillip Susi
2013-01-03 18:02 ` Alasdair G Kergon
2013-01-03 19:13 ` Stuart D Gathman
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