Re: [9fans] threads vs forks

["J.R. Mauro" <jrm8005@gmail.com>]

On Wed, Mar 4, 2009 at 12:50 AM, erik quanstrom <quanstro@quanstro.net> wrote:
>> >
>> > Both AMD and Intel are looking at I/O because it is and will be a limiting
>> > factor when scaling to higher core counts.
>
> i/o starts sucking wind with one core.
> that's why we differentiate i/o from everything
> else we do.
>
>> And soon hard disk latencies are really going to start hurting (they
>> already are hurting some, I'm sure), and I'm not convinced of the
>> viability of SSDs.
>
> i'll assume you mean throughput.  hard drive latency has been a big deal
> for a long time.  tanenbaum integrated knowledge of track layout into
> his minix elevator algorithm.

Yes, sorry.

>
> i think the gap between cpu performance and hd performance is narrowing,
> not getting wider.
>
> i don't have accurate measurements on how much real-world performance
> difference there is between a core i7 and an intel 5000.  it's generally not
> spectacular, clock-for-clock. on the other hand, when the intel 5000-series
> was released, the rule of thumb for a sata hd was 50mb/s.  it's not too hard
> to find regular sata hard drives that do 110mb/s today.  the ssd drives we've
> (coraid) tested have been spectacular --- reading at > 200mb/s.  if you want
> to talk latency, ssds can deliver 1/100th the latency of spinning media.
> there's no way that the core i7 is 100x faster than the intel 5000.

For the costs (in terms of power and durability) hard drives are
really a pain, not just for some of the companies I've talked to that
are burning out terabyte drives in a matter of weeks, but for "mere
mortals" as well. And I'm sorry but the performance of hard drives is
*not* very good, despite it improving. Every time I do something on a
large directory tree, my drive (which is a model from last year)
grinds and moans and takes, IMO, too long to do things. Putting 4GB of
RAM in my computer helped, but the buffering algorithms aren't
psychic, so I still pay a penalty the first time I use certain
directories.

Now I haven't tested an SSD for performance, but I know they are
better. If I got one, this problem would likely subside, but I'm not
convinced that SSDs are durable enough, despite what the manufacturers
say. I haven't seen many torture tests on them, but the fact that
erasing a block destroys it a little bit is scary. I do a lot of
sustained writes with my typical desktop workload over the same files,
and I'd rather not trust them to something that is delicate enough to
need filesystem algorithms to be optimized for so they don't "wear
out".

I guess, in essence, I just want my flying car today.

>
> - erik
>
>