Disk I/O as a bottleneck?

[Nadav Har'El]

On Sun, May 08, 2011, is123 at zahav.net.il wrote about "Re: Disk I/O as a bottleneck?":
> I don't agree with this setup. Regular consumer drives setup with RAID to
> stripe are going to be much, much faster and have less problems in the long
> run than single SSDs at this point as well as being a better value until
> prices change a lot.

Having two hard disks will, at best case, *double* your seek time. This is
still pretty slow, isn't it? Won't an SSD, even cheap one, have a better
random access read performance?

> Consider not using swap, because swap when in use causes a lot of thrashing
> and kills performance especially if you only have 1 or 2 drives. If you have

Even without any swap space, you can have a lot of thrashing: Clean pages -
program text (the code), shared libraries, memory-mapped files, and so on -
are simply "forgotten" when the page cache is needed for other things, and
when you get back to that other program, suddenly all its code and libraries
are not in memory, and getting them back requires a lot of random-access
reads from disk, and (especially if the disk is doing other things at the
same time) causes the program to appear "stuck" or "sluggish".

Again, I don't know if this is the sort of problem that actually bothered
the OP.

-- 
Nadav Har'El                        |        Sunday, May  8 2011, 4 Iyyar 5771
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