Re: debian installer 4k sectors
Pavel Kosina composed on 2016-04-08 08:36 (UTC+0200):
several times I tried install Debian stable/testing. I have MB Asrock
UEFI D1800B-ITX and HDD WD20EFRX. Debian installer /part where
partitioning and formatting happens/ never formats to correct sectors
4k. It always formats to 512b:
Hard disks now have 4k sectors, but PC and Mac operating systems do not. It
will probably still be quite some time, if ever, before software stops
defining a sector as 512b.
Hard disks transparently convert software (logical) sectors of 512b to 4k
internally. Smarter kernels, drivers and partitioning applications take this
need to convert into account, aligning reads and writes as much as possible
to minimize the need for internal conversion, primarily by using I/O block
sizes of 4k (8 512b sectors) or some multiple thereof, especially when
partitions are being created. By doing so, the internal overhead is
eliminated or minimized, maximizing I/O performance.
How this works and more is explained at:
linuxbox:~# fdisk -l
Disk /dev/sda: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xa10b2c0d
Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 3903531007 3903528960 1.8T 83 Linux
/dev/sda2 3903533054 3907028991 3495938 1.7G 5 Extended
/dev/sda5 3903533056 3907028991 3495936 1.7G 82 Linux swap /
Partition 2 does not start on physical sector boundary.
why is that? Is that bug or I miss something?
As noted by others, it mostly amounts to a cosmetic bug, but it can cause
other partitioning programs to report corruption of the table and refuse to
function, or even recognize the existence of partitions existing already.
Due to this there is also error: "Partition 2 does not start on physical
Software other than partitioners is more accommodating than partitioning
tools about this "error". The kernel and disk drivers are not affected by this.
You do have the option to partition in advance with a tool of your choice,
and simply direct the installer which partitions to mount where. I always do.
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words are persuasive." Proverbs 16:21 (New Living Translation)
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