SSD drives

[shimi]

On Sun, Dec 30, 2012 at 6:26 AM, Dan Shimshoni <danshimsh at gmail.com> wrote:

> Hi,
>
> 2 Questions about SSD drives:
>
> First, I would appreciate of someone who has SSD disk will
> run
> hdparm -t /dev/sda
> and post the results here. (In the spirit of the recent thread about
> HW for linux).
>
> I have
> /dev/sda:
>  Timing buffered disk reads: 586 MB in  3.01 seconds = 194.68 MB/sec
> And it interests me to compare results
>
>
>
An almost two years old Intel X25-E :

# hdparm -t /dev/sda

/dev/sda:
 Timing buffered disk reads: 714 MB in  3.01 seconds = 237.40 MB/sec

# uname -a
Linux matrix 3.6.2-gentoo #1 SMP PREEMPT Sun Oct 21 22:49:01 IST 2012
x86_64 AMD Phenom(tm) II X4 955 Processor AuthenticAMD GNU/Linux



> Does a result of, let's say, 400  MB/sec, which is double speed comparing
> the
> above result, will boost a task of building a linux kernel (on a dual
> core machine)
> in about 1.5 or 2?
>
>
I really don't think so. SSDs (IMHO) makes computer much faster due to the
VERY low seek time - the time it takes you to get a block. Compare 10-20ms
with ~0.1ms. A regular hard drive simply wastes a lost of time seeking the
data, instead of... reading it :) When you work with a lot of files,
getting to the file fast makes a tremendous difference. This is similar to
the reason why browsing websites which are close to you network-wise is
much faster - even though the bandwidth you have is the same - the
client/server latency due to the network affects the time it takes you to
negotiate (compare to 'seek') with the server the content you want. The
more objects you want, the higher the latency, the slower the site will
load. This is why using CDNs and reducing the number of HTTP requests (e.g.
by using CSS Sprites) - help a lot in speeding websites.


> Second question:
> I must admit that I am a newbie with SSD, so this question might seem
> obvoious to others:
> I saw that inner SSD disks, which are sold in stores like KSP/Ivory,
> are in laptop form factor (2.5'').
>
> Is there some reason that there are no inner 3.5'' disks for Desktops
> (there
>         are extenal SSD which can be , so I believe, used with desktops) ?
>

Hard Drives have a reason to be large - they have a platter that occupies
space. If you reduce the platter size, you need to enlarge the density, or
add more platters - which adds thickness, noise, heat, and lowers your
MTBF. Electronics nowdays are small and doesn't need all that... There's no
point in making a large chassis just for the purpose of a large chassis...



> Is there something which prevent us from connecting 2.5'' inner SSD to
> a desktop (I mean STAT2- based or SATA3-based)  ?
>
>
Not really. The SATA is the same. Your only issue is fixating the drive to
your PC chassis. Some computer cases have a special place for 2.5" drives
for SSD (like my Antec 1200). Alternatively there are 3.5"->2.5" adapters.
But learn from someone who made a mistake (me ;)) - check before you buy
that they're compatible with the screws location of the SSD.

HTH,

-- Shimi
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