[linux-lvm] LVM Alignement

[linux-lvm] LVM Alignement

[Matecki, Lukas]

[-- Attachment #1: Type: text/plain, Size: 788 bytes --]

Hey all,

i have a question about Lun / Partition alignment.
If I use LVM in a Linux guest OS on a VMFS Datastore i can align my Partitions with mbralign.
But the tool failes if I will try to use it on a LVM only VDisk. For example the second Disk of this guest OS.

Did I need to align the second disk or did LVM take care of alignment ? I just mean a single VDisk with a single LVM VG.

Greetings

Lukas Matecki

Windows Server
-------------------------
LVR-InfoKom
Ottoplatz 2
50679 Köln
Tel. 0221 809 2617
mailto:Lukas.Matecki@lvr.de
http://www.lvr.de<http://www.lvr.de/>
http://www.infokom.lvr.de<http://www.infokom.lvr.de/>

### Service Team Windows Server
### Telefon: 0221 809 7600
### Servicezeiten: 07:00 Uhr bis 16:00 Uhr
### mailto:z13win@lvr.de



[-- Attachment #2: Type: text/html, Size: 8200 bytes --]

Re: [linux-lvm] LVM Alignement

[Alexander Dalloz]

> Hey all,
>
> i have a question about Lun / Partition alignment.
> If I use LVM in a Linux guest OS on a VMFS Datastore i can align my
> Partitions with mbralign.
> But the tool failes if I will try to use it on a LVM only VDisk. For
> example the second Disk of this guest OS.
>
> Did I need to align the second disk or did LVM take care of alignment ? I
> just mean a single VDisk with a single LVM VG.
>
> Greetings
>
> Lukas Matecki

By default LVM uses an offset of 192k, see:

# vgs -o +pe_start
  VG         #PV #LV #SN Attr   VSize VFree 1st PE
  VolGroup00   1   1   0 wz--n- 8,78G    0  192,00K

Alexander

Re: [linux-lvm] LVM Alignement

[Mike Snitzer]

On Fri, Jul 22 2011 at  2:26pm -0400,
Alexander Dalloz <ad+lists@uni-x.org> wrote:

> > Hey all,
> >
> > i have a question about Lun / Partition alignment.
> > If I use LVM in a Linux guest OS on a VMFS Datastore i can align my
> > Partitions with mbralign.
> > But the tool failes if I will try to use it on a LVM only VDisk. For
> > example the second Disk of this guest OS.
> >
> > Did I need to align the second disk or did LVM take care of alignment ? I
> > just mean a single VDisk with a single LVM VG.

More recent versions of lvm will take care of alignment (e.g. that found
in fedora 14, 15 or RHEL6).

> By default LVM uses an offset of 192k, see:
> 
> # vgs -o +pe_start
>   VG         #PV #LV #SN Attr   VSize VFree 1st PE
>   VolGroup00   1   1   0 wz--n- 8,78G    0  192,00K

That was the old default.  That is not the case any more.

The default alignment (for storage that doesn't export topology
information) is now 1MB.  But that may be overriden with lvm.conf's
'default_data_alignment'.

Also see 'data_alignment_detection' in lvm.conf.

Mike