Re: Any pros or cons of using full disk versus partitons?

[Roman Mamedov <rm@romanrm.ru>]

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On Thu, 14 Apr 2011 18:11:59 +1000
NeilBrown <neilb@suse.de> wrote:

> On Thu, 14 Apr 2011 11:57:47 +0400 CoolCold <coolthecold@gmail.com> wrote:
> 
> > Just my 2 cents: I've faced problems when newer disk was smaller than
> > old disk two or three times, so using partitions now with setting some
> > free space at the end - something near 80 or 100 megabytes.

There are also some Gigabyte motherboards which like to cut off a small
portion of a disk at the end via HPA, and writing a backup of their BIOS there.
https://encrypted.google.com/search?q=gigabyte+bios+hpa
If you had your user data or mdadm metadata there, bad luck.

On earlier motherboards this was done automatically to every new disk on
SATA0, on newer ones I think it's optional and can be disabled. But anyway, I
now prefer to leave about 8 MB of space at the end of each drive
unpartitioned, just in case.

And another point, again related to buggy BIOSes: some of them seem to read
first sectors of all attached disks and expect to see an MBR-style partition
table there; and if there's something else instead (e.g. basically random
data, in case of the whole disk used for RAID), they may become confused and
lock-up at boot. I had a couple of such cases where a board would lock-up
at HDD detection with a certain drive attached, and would only boot up
properly after it was zeroed and repartitioned.

> 
> You don't need partitions to do this.  Just use the --size option to mdadm.

But then the 1.x+ metadata is still stored at the very end of the device,
which makes it vulnerable to the HPA problem described above.

-- 
With respect,
Roman

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