[ale] no putting swap on ssd

[Greg Freemyer]

On Mon, Feb 7, 2011 at 4:52 PM, Sparr <sparr0 at gmail.com> wrote:
> This is mostly bogus out-of-date information. Yes, SSDs (and other
> solid state storage like SD cards) have a limited lifetime, but it far
> exceeds their useful lifetime these days.
>
> Assume we have wear leveling, so that single sectors don't go bad prematurely.
>
> At 50 megabytes per second of continuous writing (which is insane for
> any storage device except always-on video recording), a 16GB storage
> device with a lifetime of 1 million writes means it's going to fail in
> TEN YEARS.

I guess I'm way behind the times thinking its 10,000 writes per EB.  I
just pulled up the Intel® X25-V SSD spec. to see what it is, but it
doesn't have the number of writes provided in the spec. :(

I'll assume your 1,000,000 number is right even in the "value" SSDs.

But for clarity, most storage apps have a lot of static data involved.

So let's assume the first thing I do is put 12GB of static data on
that 16GB device.  And then never write to that data again.  That
removes that 12GB from the wear-leveling equation.

So now I only have 4GB (plus some small amount of spare EBs) with
which to wear-level.

So instead of 10 years, its 2.5 years.  Next if your partition is not
properly aligned it can easily cause 2 real writes for every userspace
initiated write.    So now it's 1 1/4 years.  (New parted as an
example recommends partitions start on 1 MiB boundaries.  That should
properly align.  Parted from before Dec. 2009 tried to force alignment
on cylinder boundaries.  That would often be misaligned for SSDs.)

I'm not seriously saying you'll see SSDs simply wear out after a year
or so, but I am saying it's something to be concerned about and plan
around or you may inadvertently find yourself behind the 8-ball.

Greg