On Fri, 4 Feb 2000, Piete Brooks wrote:
> > I've got two different ide-disks in my system:
> > /dev/hda --> 6,4GB SAMSUNG SV0644A 11.90 MB/sec
> > /dev/hdb --> 13.2GB WDC WD136BA 22.22 MB/sec
>
First i would suggest that you put each disk to separate
channel. hdb --> hdc.
> You aren't going to get on all that well !
>
Not necessarily that bad..read on.
> > Now my question, is it actual to make nearly same sized partitions to use
> > with RAID-1,
>
> Missing `necessary' maybe ?
>
<stuff deleted>
>
> > how does this touch the performance of my disks ?
>
> Unfortunately, all writes will be slowed down to the slower of the two, i.e.
> 12MB/s :-(
> There are patches out there to make RAID1 reads into RAID0 reads -- you *may*
I don't exactly know what you mean by making RAID1 reads into RAID0 reads.
Do you mean RAID 10 configuration by this ?
Could you provide links to those patches ? One is atleast
in <http://www.iki.fi/miku/raid1>
> be able to get them, and tweak them so that it knows to actually read 1/3rd of
> the data off the slow disk, and 2/3rds off the fast disk ... Fun !!
>
I would say that the overall performance gain would be
noticeable and worthwhile, even without this kind of weighted
read balancer. Ofcourse the other disk is twice as slow what comes to
throughput performance, but it certainly is not twice as slow
when it comes to seek speeds. Prolly just 20-30%
So in effect he would gain almost double amount of seeks / sec,
which would greatly improve overall io performance. Typically accesses to
disk in 'normal' usage are scattered, sometimes even if you read a
single file sequentially. So unless you are a streaming one
big video mpg out, you can say that your io is as much seeking as it
is reading/writing. In other words io performance is function of both
throughput and seeks and you should keep _both_ in mind.
What i would like to see more in this list is that when folks
submit their performance figures, instead of just putting MB/sec
there would be seeks/sec also =)
That would allow us to see the strenghts and weaknesses of
different raid systems more accurately and thus we could select the
correct setup to our specific need.
Briefly: seeks _DO_ matter :)
-- Mika <[EMAIL PROTECTED]>
