FreeBSD on SSD on ASUS P5KPL-C
Warren Block
wblock at wonkity.com
Fri Nov 23 05:56:58 UTC 2012
On Fri, 23 Nov 2012, Shane Ambler wrote:
> On 22/11/2012 14:49, Warren Block wrote:
>> On Wed, 21 Nov 2012, Warren Block wrote:
>>
>>> Got a chance to set up a scratch drive and check this. Turns out
>>> I left out the step of creating a "slice" (MBR partition) to hold
>>> the FreeBSD partitions. Also, GPT labels cannot be used in an
>>> MBR. Fixed below. I will probably add this to my disk setup
>>> article because it has come up more than once.
>>
>> The fdisk/bsdlabel section of my disk setup article has been
>> rewritten to use gpart. Feedback welcome.
>>
>> http://www.wonkity.com/~wblock/docs/html/disksetup.html
>
> Something I meant to ask before - is there any benefit to following the
> steps described in
> http://www.aisecure.net/2012/01/16/rootzfs/
My guide is based on using UFS. ZFS or other filesystems will also
benefit from block alignment, but the methods to get there can be
different.
> The step of using gnop is meant to trick zfs into believing the disk has
> 4K sector size to improve performance, which I would think zfs would be
> able to figure out by talking to the disk.
Unless ZFS is put on a bare, unpartitioned disk, configuration for
performance is better left to the user. It's a pain to correct
automatic configs when they guess wrong.
> Does partitioning hide the sector size or would the step of aligning
> the partition start to a 4k sector unhide the 4k size?
> Or are these steps just a waste of time?
It's not about hiding the device's native block size, it's about getting
the filesystem to do aligned I/O so the device can just read or write
a single 4K block instead of part of one and part of another.
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