Re: kernel: device-mapper: table: 254:1: adding target device sda1 caused an alignment inconsistency
On Sat, 28 Jul 2018, David Wright wrote:
> On Sat 28 Jul 2018 at 10:57:45 (-0300), Henrique de Moraes Holschuh wrote:
> > On Sat, 28 Jul 2018, Rick Thomas wrote:
> > > > rbthomas@small:~$ lsblk -t
> > > > NAME ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED RQ-SIZE RA WSAME
> > > > sda 0 4096 33553920 4096 512 1 mq-deadline 60 128 0B
> > > > `-sda1 0 4096 33553920 4096 512 1 mq-deadline 60 128 0B
> > > > |-small-swap -1 4096 0 4096 512 1 128 128 32M
> > > > |-small-root -1 4096 0 4096 512 1 128 128 32M
> > > > `-small-home -1 4096 0 4096 512 1 128 128 32M
> > > > mmcblk2 0 512 0 512 512 0 mq-deadline 128 128 0B
> > > > |-mmcblk2p1 0 512 0 512 512 0 mq-deadline 128 128 0B
> > > > `-mmcblk2p2 0 512 0 512 512 0 mq-deadline 128 128 0B
> > > > rbthomas@small:~$
> > >
> > > Note the alignment values of “-1” for the lvm entries but not for the GPT partition or the whole disk.
> > > Why do you suppose that is?
> >
> > Keep in mind that you *offset*-align the outer container *only*, and then inside
> > you just keep the size alignment.
> >
> > So, the above ensures correct use of the partitions even if sda1 is
> > unaligned.
> >
> > If you offset-align sda1 to -1, everything inside it should have an offset of
> > zero to keep the alignment correct.
>
> I don't think I fully understand the explanation. Can you point out
> the number(s) that's wrong, and how it should be corrected.
There is nothing wrong on the table above as far as I can tell,
*assuming* the device does need the -1 alignment. Since sda1 isn't
aligned, everything inside it at the first level must be (and is)
aligned at -1 to compensate.
Where sda1 aligned at -1, nothing inside it should be, as sda1 would
already provide the required alignemnt to anything inside it.
> (To which number does the -1 apply, and what units is it in?)
It applies to whatever line it is listed, and it is in "host-side
sectors" (512 bytes in this case), where "host" is "your computer" as
opposed to "the HDD".
No idea why your USB-connected HDD is causing the warnings. I didn't
think there were still devices in the market with that dreadful "windows
workaround" (which not even windows want, nowadays)... but USB-connected
HDDs are *always* suspect of insanity caused by crap protocol bridges,
so YMMV.
--
Henrique Holschuh
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