On Apr 27, 2014, at 2:54 AM, Andrei POPESCU <andreimpope...@gmail.com> wrote:
> On Sb, 26 apr 14, 20:24:12, Rick Thomas wrote:
>>
>> With more and more disks being manufactured with "Advanced format"
>> (4096-byte physical-sectors) I'm wondering how I can tell the
>> Debian-installer partitioner to align all partitions on 4096-byte (or
>> 1 MiB for FLASH) boundaries? Is there some parameter I can pre-seed
>> -- or set at runtime?
>
> The wheezy installer (at least) aligns by default to 1MiB.
I haven't been able to test this on x86 or amd64, but on powerpc64 this doesn't
seem to be true.
I just did a fresh install from the Wheezy PowerPC DVD-1 on an Apple PowerMac
G5. When it got to disk partitioning, I specified "use the full disk and
create LVM" with a separate LV for /home. The following is what the partition
table looks like:
root@bigal:~# mac-fdisk -l /dev/sda
/dev/sda
# type name length base (
size ) system
/dev/sda1 Apple_partition_map Apple 63 @ 1 (
31.5k) Partition map
/dev/sda2 Apple_Bootstrap untitled 1954 @ 64
(977.0k) NewWorld bootblock
/dev/sda3 Apple_UNIX_SVR2 untitled 500001 @ 2018
(244.1M) Linux native
/dev/sda4 Linux_LVM untitled 1953023100 @ 502019
(931.3G) Unknown
/dev/sda5 Apple_Free Extra 49 @ 1953525119 (
24.5k) Free space
Block size=512, Number of Blocks=1953525168
DeviceType=0x0, DeviceId=0x0
When I say "sector" or "logical-sector" in the following I mean 512-byte
sector. When I say "physical-sector" I mean 8 logical-sectors (4096-bytes).
When I say "megabyte" or "MiB" I mean 1048576 bytes or 2048 logical-sectors, or
256 physical-sectors.
The Apple_partition_map (sda1) is fine. It skips the 0th sector and ends on
the 64 sector (8 physical-sector) boundary.
But the Apple_Bootstrap/NewWorld_bootblock partition (sda2), while it begins on
a physical-sector boundary, does not end on a physical-sector boundary. A
reasonable thing for the installer to do would be to make it exactly 1 megabyte
long, but I'd be happy with any integer number of physical-sectors. The
openboot firmware is expecting it to be just about anything longer than 800k
(100 physical-sectors / 400 logical-sectors) It doesn't know anything about
physical-sectors vs logical-sectors, so as long as the simulation in the
diskdrive works, so will the openboot firmware. It only gets used when the
system boots or a new yaboot.conf gets installed, so this is not critical, but
it is curious. Perhaps the installer thinks that a full MiB is too large? I
can imagine that this might be true on some of the IBM hardware, but I know
it's not true for Apple hardware. In any case...
The third partition (sda3) holds /boot for the installed Linux. It does not
start or end on a physical-sector boundary (due to the odd length of the
preceding partition), though there is no reason I can think of that it needs to
be that way. Again, this partition is not used frequently, so not starting on
a MiB boundary does not noticeably affect performance -- but it is odd,
nevertheless. However, there is absolutely *no* excuse for it not to *end* on
a MiB boundary. Indeed, the rather strange length seems to be chosen
specifically to keep it from ending on a MiB boundary. Curiouser and curiouser!
Now we come to the really strange one -- the Linux_LVM (sda4) partition. There
really is no excuse for it not to start on a clean MiB boundary, and every
reason to assume that it should. And yet... here we are with a starting sector
that is not even a multiple of 2, let along a multiple of 2048)!
So I ask again: Aside from doing the partitioning manually, myself, is there
any way to get the installer's partitioner to respect the new guidelines for
"Advanced Format" and SSD/flash disks?
Thanks!
Rick
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