Re: Summary: Moving /tmp to tmpfs makes it useless
Serge wrote:
> 2012/6/10 Uoti Urpala wrote:
> > You've posted blatantly false claims. If you post claims like "1+1
> > equals 2 because the moon is made of cheese", then you're a moron, even
> > if 1+1 does equal 2.
>
> (I like this example :)) It could be, it's impossible to know everything
> in the world, I can be wrong. What false claim are you talking about?
The problem is that you've posted quite a few of those false claims, and
don't seem a have a clear distinction between things you actually know
and things you only have a vague guess about. You seem to make claims
about both equally.
For example, the page you linked for your "SSDs can take 50 years of
writing before they wear out" claim has a first paragraph saying
durability IS again an issue - much more so than it was in 2007 when the
original article with the "50 years" claim was written (and even then
that seems to have been some particularly durable high-end server
hardware).
As another example, this part from your FAQ is nonsense:
> When you
> read from ext3, the oldest part of the filecache is dropped and data is
> placed to RAM. But reading from swap means that your RAM is full, and in
> order to read a page from swap you must first write another page there.
> I.e. sequential read from ext3 turns into random write+read from swap.
There is no such difference reading from a normal filesystem or reading
from swap. Iterating reads from swap can trigger writes, but if that's
what you're referring to here, you've clearly either failed to
understand what actually happens or are writing a very misleading
description.
> >> Do you dismiss the theory (confirmed by Uoti Urpala test script) that
> >> tmpfs+swap INCREASE number of writes and are hence bad for SSD?
> >
> > I think what the script shows is that there can be significant problems
> > using tmpfs to hold large amounts of data, even if you have a lots of
> > swap so that running out is not an issue. It doesn't show that the
> > number of writes would increase on average.
> >
> > In general you seem to be quite clueless about the actual behavior of
> > cache/swap, but you've still continued to make various claims about it.
>
> I was referencing your words:
Yes, I did say that it can generate writes in some circumstances.
However, that does not imply your "tmpfs increases writes" claim in
general. In what has been a default installation, I think you'd normally
start hitting the tmpfs size limit before the problematic behavior shown
by the script would become a serious issue. It mainly shows that "make
the size limits bigger" may not be a good solution to the space issue.
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