[ale] 2 questions memory related

[Scott Castaline]

On Thu, Jun 16, 2011 at 10:08 PM, Michael B. Trausch <mike at trausch.us>wrote:

> On 6/16/2011 8:01 PM, Scott Castaline wrote:
> > 1. Just had 1 stick 2GB of RAM go bad. I had originally bought as part
> > of a set of 4 sticks for a total of 8GB. My question is how critical
> > is it to buy in matched sets? Couldn't I buy just a replacement for
> > that stick? I don't overclock so I don't push them so I can't see
> > where I have to have handpicked memory. I would plan on getting the
> > same exact mfg part on a single stick basis.Am I wrong tinking this way?
>
> You should be fine ordering the part separately. The only thing that you
> need to be sure of is that you match the specs of the memory that is in
> the system currently.
>
> > 2. I am currently running dd if=/dev/urandom of=/dev/sde on a new 2TB
> > drive. I was logged into my GUI desktop (KDE) and after several hours
> > my desktop started disintegrating and window apps were becoming
> > unrecognisable, but I was able to close ot most of them. I switched
> > over to one of the text VTs and top was reporting that out of 4GB of
> > RAM I only had less than 500MB available and I was starting to use
> > swap. I've done this in the past with only 4GB of RAM on different
> > hardware and earlier version of Fedora, without any problems like
> > this. I'm not doing anything that different than in the past. My
> > question is, what command(s) would tell me what is actually hogging
> > all of the RAM? I don't want to kill the process as I'm anticipating
> > it aking about 4 days to complete. At least on a 2 core AMD it toke
> > about 44 hours for 1TB, I'm not sure how much quicker a 4 core
> > processor will do this. I was also running 800MHz RAM then, now I'm
> > running 1333MHz RAM of course I realize that that is not the real
> > speed of the bus clock.
>
> The 'dd' process is not going to run (significantly) differently on a
> multicore/multiprocessor system than on a unicore/uniprocessor system;
> nor would it likely if it were written to be a multithreaded program.
> The reason is that bandwidth limitations are going to be the bottleneck
> of the command. Even on a system that can generate pseudorandom bytes
> more quickly, the hard disk drives are going to be the limiting factor.
>
> In order to find out which process is hogging memory, I'd recommend
> "htop". Be sure to sort the output by the MEM% column.
>
>     --- Mike
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Will htop give me much different results than top? I found on top sorting by
%mem that mysqld was at 1.0 which in my opinion is not a hog, but I'm not
sure why it is there as I didn't install mysql unless some other app usees
it. Also is it possible that it's not just a process but several processes
used to do a certain task. I have noticed several proceses named khelper?
where the ? is a different number for each one and there were others like
that. I don't remember seeing these in earlier versions of Fedora.

Also any recommendations on memory brands/model?
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