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Date: Fri, 17 Feb 2012 11:15:40 -0800
From: Julian Elischer <julian@freebsd.org>
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To: Alexander Best <arundel@freebsd.org>
References: <20120217141607.GA63659@freebsd.org> <4F3E9A14.3070605@freebsd.org>
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Cc: freebsd-fs@freebsd.org
Subject: Re: freebsd-swap on ssd
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On 2/17/12 11:09 AM, Alexander Best wrote:
> On Fri Feb 17 12, Julian Elischer wrote:
>> On 2/17/12 6:16 AM, Alexander Best wrote:
>>> hi there,
>>>
>>> putting a freebsd-ufs partition on an ssd isn't recommended, since the ufs
>>> structure (unlike zfs e.g.) requires certain data to be continuously
>>> written to
>>> a fixed location and thus will cause the ssd to quickly run out of
>>> write-cycles
>>> and die.
>> nonsense.
>> the SSD doesn't use the same flash for the same logical locatio each time!
>> it maps it to different locations each time.
> i simply repeated what kirk mckusick said in the SU+J introduction video. he
> said for exactly this reason ufs should not be used on an ssd, since stuff like
> inode entries live in a fixed location, whereas with zfs the ueberblock can
> live in 128 locations. also in case of SU+J, where the journal only takes up a
> very small part of the disk due to the fact that it's only tracking metadata
> changes and isn't doing logging (like gjournal), there's also the chance to run
> out of write-cycles.
I think he meant ON A RAW FLASH DEVICE
SSD's have all that taken care of transparently.

There are special file systems for raw flash devices that take all 
that into account,
and ffs is not one of them.