Re: Wheezy Installer Auto-Partition Oddity
----- Original Message -----
> From: Mark Allums <mark@allums.com>
> To: 'Debian User' <debian-user@lists.debian.org>
> Cc:
> Sent: Sunday, January 6, 2013 1:26 PM
> Subject: RE: Wheezy Installer Auto-Partition Oddity
>
>
> [snip]
>>
>> So, again I ask: Why that 1MiB unpartitioned space before the beginning
> of
>> a new partition? Both Debian 6 and 7 installer partitioner insert it
> (when
>> you choose Auto-partition; don't know whether it does with Custom) as
>> does gparted (Discovered that when I resized three existing contiguious
>> primary partitions [no gaps added after resizing] and added two new
> logical
>> partitions [gaps added automatically] on a 7 year old 512 byte sector
> 160GB
>> drive). Got to be a reason. I don't think it's a bug.
>
> You are correct, there is a reason. Previously, I said that LVM needs it.
> I read something that explained it, but I may have misremembered what I
> read. Perhaps it had something to do with RAID, perhaps it was something
> else. I remember several different web sites telling me to leave space,
> although I seem to recall that they were Ubuntu-related.
I haven't been able to find anything other than my vague recollection of it being mentioned as to why LVM needs the unpartitioned gaps, if it needs it. LVM has worked without them for years. I've been told that LVM doesn't write anything to those gaps. So, that can't be the reason to have them. Maybe, it's a GPT thing even if you're not using one? Or a safeguard against overlapping huge partitions?
> However, there is also a performance gain to be had when aligning partitions
> to 1MB boundaries. This is true for both 512- and 4096-byte sectors. Of
> course, since both 512 bytes and 4096 bytes divides evenly into 1MB, adding
> at least 1MB before and after the partition kills two birds with one stone.
> This I read on the GParted forums.
I understand the need to align partitions particularly when dealing with RAIDed drives. It's just that I thought partitioning utilities for some years now have automatically aligned partitions. However, I've never noticed 1MiB gaps until recently. Of course, I have always manually partitioned in cylinders.
> At any rate, let the tool add the space; it even will calculated the correct
> size and sector alignment for you. It may be untidy, but it does no harm.
It's not that a megabyte here or there is lost. It's the not knowing "why" that's bothersome.
B
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