[colug-432] SSD vs SD

[Rick Hornsby]

On Sun, Mar 17, 2013 at 9:24 AM, Matt Simmons <standalone.sysadmin at gmail.com
> wrote:

> There are a lot.
>
> First, lets talk about what they have in common.
>
> Both use flash memory.
>
> OK, now lets talk about the differences.
>

...

Really interesting stuff, thanks for the insight!  Definitely have a much
better understanding of how an SSD actually works and what makes it
different than what we're used to thinking about in terms of storage.


> Another big factor is data retention.The underlying way that flash
> memory writes is essentially to put an electrical charge into a small
> deposit of doped silicon. Over time (months typically), if left
> unrefreshed, that electrical charge will dissipate and the controller
> won't be able to determine whether the bit is a one or a zero. For
> this reason, SSD controllers periodically go through the old data and
> "scrub" it, refreshing the electrical charge. This is really hard to
> do if the flash chip is on a USB keychain in your backpack.
>

Hmm.  Interesting.  So would a logical conclusion to this be that archival
storage on an SSD is not recommended?  As in, for example, don't stick an
ssd into an external storage bay, throw it in the closet and expect the
data to be readable in a year?  Also, don't stick an ssd into a system that
you only use (and then power down) a couple of times/month (or less
frequently)?  Basically - the SSD needs power.

This is definitely one area of SSD storage theory that I was completely
unaware of.

Several folks that I've talked to have said that they install their OS and
programs onto their SSD and put everything else onto spinny storage (what
is the right term to reference a spinning disk to differentiate it from an
SSD?).  I bought an SSD to take a completely different approach - I left my
OS, applications, etc where they were.  I use the SSD as a sort of
temporary storage for my Adobe Premiere video editing projects.  Once the
project has been completed and delivered to the client, I move it to
"permanent" storage on the spinning disk.  Outside of nonsense I've dealt
with for many, many years with Premiere, as has traditionally been the
case, disk i/o seems to be the biggest bottleneck with today's
multi-processor, multi-core, 10+ gigs of memory systems.

It seems like by putting the OS on your SSD, you get a sort of narrow
benefit - most of the libraries are loaded into memory on boot and
obviously are never written to during the normal course of operations.
 Most of your performance advantage is then at boot time, and you're back
to the slower read/write times thereafter.  Obviously, I'm using mine for a
pretty narrow case as well, but I've also got a very specific use case in
mind.

How are others taking advantage of the SSD performance?  I assume that most
of us either have an SSD in our laptops or are mixing them with spinning
disks in desktop systems.
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