On Fri, 1 Jun 2012, Victor Sudakov wrote:
Warren Block wrote:
I have installed 9.0-RELEASE on a SSD drive with the following
tweaking so far:
1. tmpmfs="YES" (WRKDIRPREFIX etc will go there too).
2. mount -o noatime
3. tunefs -t enable
I have not done any tricky partition alignment, do I really need to? Is
anything else advisable?
If it's not aligned, there can be a pretty significant performance
drop. Please show the output of 'gpart show' on that drive if it's GPT
(gpart show ada0) or drive and slice if it's MBR/bsdlabel (gpart show
ada0 && gpart show ada0s1).
It was created by the "Auto" option of the new FreeBSD installer:
[sudakov@vas ~] gpart show ada0
=> 34 117231341 ada0 GPT (55G)
34 128 1 freebsd-boot (64k)
162 111148928 2 freebsd-ufs (53G)
111149090 5861376 3 freebsd-swap (2.8G)
117010466 220909 - free - (107M)
That is not aligned, either with 4K or 1M:
(162*512)/4096 = 20.25
If the performance is good enough, leave it alone. Use
# diskinfo -tv /dev/ada0p2
to get an optimistic version, or do some in-depth benchmarking with
benchmarks/bonnie++.
To get it aligned, back up and repartition:
(Back up first!)
# gpart destroy -F ada0
# gpart create -s gpt ada0
# gpart add -t freebsd-boot -s 512k ada0
# gpart bootcode -b /boot/pmbr -p /boot/gptboot -i1 ada0
# gpart add -t freebsd-ufs -b 1m -s 53G ada0
# gpart add -t freebsd-swap ada0
That creates a 512k boot partition which allows for growth of the boot
code. Then the UFS partition starts at 1M, an even multiple of both 4k
and 1M for alignment, and a common semi-standard. Then swap fills out
the drive; that could be reduced by giving a -s size if you want to
leave that 107M at the end for something else.
(gpart's -a option is not used. It isn't needed here, and overrides the
-b option in earlier versions of gpart.)
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