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Re: wiki about block alignment issues



Daniel Pocock <daniel@pocock.pro> wrote:

> I've started a wiki about block alignment issues:

> https://wiki.debian.org/DiskBlockAlignment

> Can anybody comment on specific packages / tools that may help people
> investigate or update their systems, maybe adding links to the wiki?

There is also an interesting "wrinkle" in the way the Debian installer
lays out logical partitions in an extended partition.

The extended partition will be _not_ aligned but offset, so that the
logical partition (which contains the file system) is then correctly
aligned.

You have to keep that in mind, when looking at such a partition table
with fdisk and calculating the alignment for the partitions.

The extended one being unaligned is without consequences, because it
does not directly contain the data but is just a mere container for the
logical partition, which is correctly aligned.

Example:

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048    40105983    20051968   83  Linux
/dev/sda2        40108030    41940991      916481    5  Extended
/dev/sda5        40108032    41940991      916480   82  Linux swap / Solaris

sda2 -> 40108030/4096 -> 9791.99951171875 -> offset by 2 sectors to the front
sda5 -> 40108032/4096 -> 9792 (aligned correctly)

Grüße,
Sven.

-- 
Sigmentation fault. Core dumped.


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