9.1 RELENG_9 Unable to cleanly dismount root partition on
wblock at wonkity.com
Mon Aug 27 20:16:08 UTC 2012
On Mon, 27 Aug 2012, Kevin Oberman wrote:
>> No obvious problems jumped out at me. Here are my notes:
>> The gpart version is halfway down. I really need to switch that around.
> Pretty good page, but I would really suggest that you also do either
> 4k or 1M alignment on your partitions. If you don't and use a disk
> with 4K blocks (internally), you will have terrible performance.
You mean add the -a parameter for gpart? All that -a does is round
partition starting blocks and sizes to even values. If the numbers
given are already even multiples, it does nothing.
The reason -a4k is not shown there is because until a few months ago, -a
overrode -b. So
# gpart add -t freebsd-ufs -l gprootfs -a4k -b 1M -s 2G da0
did not start that partition at 1M, but instead at the next even 4K
block after the first 512K partition; block 1064 instead of block 2048,
AFAIR. The fix to gpart (thanks to ae@) is in 9-stable and 9.1, but not
Mentioned a little farther down in the article is that keeping
additional partitions to even multiples of 1M or 1G size will keep them
> 1M is recommended by Microsoft and used by Windows, but seems a bit
> excessive to me.
Also by some Sun RAID controllers and other systems. 1M is a nice even
multiple of a lot of common block sizes.
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