* [linux-lvm] Non 512 byte sectors
@ 2012-12-13 15:23 Phillip Susi
2012-12-14 18:52 ` Stuart D Gathman
2012-12-14 19:29 ` Mike Snitzer
0 siblings, 2 replies; 6+ messages in thread
From: Phillip Susi @ 2012-12-13 15:23 UTC (permalink / raw)
To: LVM general discussion and development
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Is it possible to get dm to report > 512 byte sector size? If so, how?
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Non 512 byte sectors
2012-12-13 15:23 [linux-lvm] Non 512 byte sectors Phillip Susi
@ 2012-12-14 18:52 ` Stuart D Gathman
2012-12-14 19:29 ` Mike Snitzer
1 sibling, 0 replies; 6+ messages in thread
From: Stuart D Gathman @ 2012-12-14 18:52 UTC (permalink / raw)
To: linux-lvm
On 12/13/2012 10:23 AM, Phillip Susi expounded in part:
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> Is it possible to get dm to report > 512 byte sector size? If so, how?
>
>
blockdev --getss /dev/vg/lv (or any other block device)
That is probably logical sector size, however. The only way I know to
get physical sector size is:
hdparm -I /dev/sda
which reports logical and physical sector size. Some WD devices are
known to lie about physical sector size, however.
If you always align stuff to 4096, there won't be a problem. In fact,
new technology tends to have much larger alignment requirements for
optimum performance - say 128k, the size of an erase block, or 64k for a
RAID chunk size. So aligning everything to 1M should hold you for a while.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Non 512 byte sectors
2012-12-13 15:23 [linux-lvm] Non 512 byte sectors Phillip Susi
2012-12-14 18:52 ` Stuart D Gathman
@ 2012-12-14 19:29 ` Mike Snitzer
2012-12-14 19:56 ` Phillip Susi
1 sibling, 1 reply; 6+ messages in thread
From: Mike Snitzer @ 2012-12-14 19:29 UTC (permalink / raw)
To: Phillip Susi; +Cc: LVM general discussion and development
On Thu, Dec 13 2012 at 10:23am -0500,
Phillip Susi <psusi@ubuntu.com> wrote:
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> Is it possible to get dm to report > 512 byte sector size? If so, how?
DM will automatically stack the physical and logical sector sizes based
on the devices that are assembled into the DM device.
So if you create an LV on a 4K device the associated DM device will
report the same physical and logical block size. You can verify as much
by looking at:
/sys/block/dm-X/queue/physical_block_size
/sys/block/dm-X/queue/logical_block_size
There are more details about IO limits stacking here:
http://people.redhat.com/msnitzer/docs/io-limits.txt
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Non 512 byte sectors
2012-12-14 19:29 ` Mike Snitzer
@ 2012-12-14 19:56 ` Phillip Susi
2012-12-14 20:10 ` Mike Snitzer
0 siblings, 1 reply; 6+ messages in thread
From: Phillip Susi @ 2012-12-14 19:56 UTC (permalink / raw)
To: Mike Snitzer; +Cc: LVM general discussion and development
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On 12/14/2012 2:29 PM, Mike Snitzer wrote:
> On Thu, Dec 13 2012 at 10:23am -0500, Phillip Susi
> <psusi@ubuntu.com> wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
>>
>> Is it possible to get dm to report > 512 byte sector size? If
>> so, how?
>
> DM will automatically stack the physical and logical sector sizes
> based on the devices that are assembled into the DM device.
Yes, but what if I am using two physical disks with 512 byte sectors,
but want the dm to appear to have 2048 byte sectors?
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Non 512 byte sectors
2012-12-14 19:56 ` Phillip Susi
@ 2012-12-14 20:10 ` Mike Snitzer
2012-12-14 22:05 ` Phillip Susi
0 siblings, 1 reply; 6+ messages in thread
From: Mike Snitzer @ 2012-12-14 20:10 UTC (permalink / raw)
To: Phillip Susi; +Cc: LVM general discussion and development
On Fri, Dec 14 2012 at 2:56pm -0500,
Phillip Susi <psusi@ubuntu.com> wrote:
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> On 12/14/2012 2:29 PM, Mike Snitzer wrote:
> > On Thu, Dec 13 2012 at 10:23am -0500, Phillip Susi
> > <psusi@ubuntu.com> wrote:
> >
> >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
> >>
> >> Is it possible to get dm to report > 512 byte sector size? If
> >> so, how?
> >
> > DM will automatically stack the physical and logical sector sizes
> > based on the devices that are assembled into the DM device.
>
> Yes, but what if I am using two physical disks with 512 byte sectors,
> but want the dm to appear to have 2048 byte sectors?
DM has no role in fabricating devices with artificial limits.
What do you hope to accomplish with this?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Non 512 byte sectors
2012-12-14 20:10 ` Mike Snitzer
@ 2012-12-14 22:05 ` Phillip Susi
0 siblings, 0 replies; 6+ messages in thread
From: Phillip Susi @ 2012-12-14 22:05 UTC (permalink / raw)
To: Mike Snitzer; +Cc: LVM general discussion and development
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On 12/14/2012 3:10 PM, Mike Snitzer wrote:
> DM has no role in fabricating devices with artificial limits. What
> do you hope to accomplish with this?
I am trying to fix dmraid on pdc arrays that are > 2TB. It seems that
pdc has the virtual disk use a larger sector size so that you can
partition it with MBR.
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^ permalink raw reply [flat|nested] 6+ messages in thread
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2012-12-13 15:23 [linux-lvm] Non 512 byte sectors Phillip Susi
2012-12-14 18:52 ` Stuart D Gathman
2012-12-14 19:29 ` Mike Snitzer
2012-12-14 19:56 ` Phillip Susi
2012-12-14 20:10 ` Mike Snitzer
2012-12-14 22:05 ` Phillip Susi
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