"swap" partition leads to instability?

[Michael Sierchio]

The Intel SLC mSATA drives I use in embedded devices don't support TRIM,
but - it doesn't seem to matter.  Actually, I'm confident that just using
bare partitions for swap is fine, and I haven't had any of the trouble I
witnessed with MLC devices.  The difference is that the size is limited to
under 32GB.

- M


On Sun, May 26, 2013 at 4:32 PM, Warren Block <wblock at wonkity.com> wrote:

> On Sun, 26 May 2013, Polytropon wrote:
>
>  On Sun, 26 May 2013 16:09:06 +0700, Erich Dollansky wrote:
>>
>>> Hi,
>>>
>>> On Sun, 26 May 2013 01:58:32 -0700 (PDT)
>>> "M. V." <bored_to_death85 at yahoo.com> wrote:
>>>
>>>  I have a 24/7 network server/gateway with FreeBSD-8.2 on a SSD drive.
>>>> it's partitioned as normal (/ , /tmp, /var , /usr and swap) for a
>>>> long time now. But recently I heard from a FreeBSD expert that I
>>>> shouldn't have swap partition for my server, and having swap
>>>> partition could make my server unstable. this was so strange for me,
>>>> and I searched a lot but couldn't find a reason for this claim.
>>>>
>>>>  because it is a false claim. I never ever have had any system with
>>> working hard, that gave a problem because of the swap space.
>>>
>>
>> I think the "problem" here is that he's using a SSD.
>> As soon as the swap partition is being in heavy use,
>> which means it receives many writes, this may lead
>> to the SSD "wearing out", decreasing its lifetime.
>>
>
> Another problem with SSDs is that they can have difficulty with wear
> leveling.  This is even worse with swap because there is no way to use TRIM
> to tell the SSD about blocks that have been freed.
>
> The workaround is a swapfile on UFS with TRIM enabled.  It works fine, and
> even better when you update the rc scripts for shutdown.
>
> Here's an article on setup:
> http://www.wonkity.com/~**wblock/docs/html/ssd.html<http://www.wonkity.com/~wblock/docs/html/ssd.html>
>
> And here is the PR with a patch:
> http://www.freebsd.org/cgi/**query-pr.cgi?pr=bin/168544<http://www.freebsd.org/cgi/query-pr.cgi?pr=bin/168544>
>
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