[dm-crypt] (More) Questions about LUKS / LVM

Milan Broz mbroz at redhat.com
Tue Sep 20 20:19:54 CEST 2011


On 09/20/2011 08:06 PM, Karl O. Pinc wrote:
> Performance is also going to suck if you don't get
> alignment right on drives with 4Kb sectors.

Data area for LUKS was always aligned to 4k offset, so
you should never see problem here.
(Underlying disk partitioning is another issue of course.)

> 
> FWIW here are the links I use to deal with 4Kb sector issues.
> 
> http://ata.wiki.kernel.org/index.php/ATA_4_KiB_sector_issues
(down, for the same reason like all kernel.org services...)

> http://lists.debian.org/debian-user/2011/01/msg02021.html

Not completely up to date. Almost all tools actively use topology
information (from kernel) or default to 1MiB alignment.
(fdisk, parted, lvm, cryptsetup, mdadm, etc)

I would say - if you are using recent distro, you have aligned
this correctly by default (when creating new storage stack).
Do not try to use any magic options, only do this if you are
sure that default result is wrong.
(And report bug if you see it with new versions of tools,
storage people spent a lot of time fixing to work it correctly.)

Milan


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