(SOLVED) Re: installing FreeBSD 8 on SSDs and UFS2 - partition alignment, block sizes, what does one need to know?

[Ronald Klop]

On Fri, 15 Jan 2010 17:57:03 +0100, Dan Naumov <dan.naumov at gmail.com>  
wrote:

> On Fri, Jan 15, 2010 at 6:38 PM, Rick Macklem <rmacklem at uoguelph.ca>  
> wrote:
>>
>>
>> On Tue, 12 Jan 2010, Dan Naumov wrote:
>>
>>> For my upcoming storage system, the OS install is going to be on a
>>> 80gb Intel SSD disk and for various reasons, I am now pretty convinced
>>> to stick with UFS2 for the root partition (the actual data pool will
>>> be ZFS using traditional SATA disks). I am probably going to use GPT
>>> partitioning and have the SSD host the swap, boot, root and a few
>>> other partitions. What do I need to know in regards to partition
>>> alignment and filesystem block sizes to get the best performance out
>>> of the Intel SSDs?
>>>
>> I can't help with your question, but I thought I'd mention that there
>> was a recent post (on freebsd-current, I think?) w.r.t. using an SSD
>> for the ZFS log file. It suggested that that helped with ZFS perf., so
>> you might want to look for the message.
>>
>> rick
>
> I have managed to figure out the essential things to know by know, I
> just wish there was a single, easy to grasp webpage or HOWTO
> describing and whys and hows so I wouldn't have had had to spend the
> entire day googling things to get a proper grasp on the issue :)

Maybe you can copy-paste your e-mail in a wiki somewhere. And your wish  
has come true for other peoples.

Ronald.



> To (perhaps a bit too much) simplify things, if you are using an SSD
> with FreeeBSD, you:
>
> 1) Should use GPT
>
> 2) Should create the freebsd-boot partition as normal (to ensure
> compatibility with some funky BIOSes)
>
> 3) All additional partitions should be aligned, meaning that their
> boundaries should be dividable by 1024kb (that's 2048 "logical blocks"
> in gpart). Ie, having created your freeebsd-boot, your next partition
> should start at block 2048 and the partition size should be dividable
> by 2048 blocks. This applies to ALL further partitions added to the
> disk, so you WILL end up having some empty space between them, but a
> few MBs worth of space will be lost at most.
>
> P.S: My oversimplification was in that MOST SSDs will be just fine
> with a 512 kb / 1024 block alignment. However, _ALL_ SSDs will be fine
> with 1024 kb / 2048 block alignment.
>
>
> - Sincerely,
> Dan Naumov
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