Re: which raid level gives maximum overall speed? (raid-10,f2 vs. raid-0)

[Bill Davidsen <davidsen@tmr.com>]

Janek Kozicki wrote:
> Hello,
>
> Yes, I know that some levels give faster reading and slower writing, etc.
>
> I want to talk here about a typical workstation usage: compiling
> stuff (like kernel), editing openoffice docs, browsing web, reading
> email (email: I have a webdir format, and in boost mailing list
> directory I have 14000 files (posts), opening this directory takes
> circa 10 seconds in sylpheed). Moreover, opening .pdf files, more
> compiling of C++ stuff, etc...
>
>   
In other words, like most systems, more reads than writes. And while 
write can be (and usually are) cached and buffered, when you need the 
next bit of data the program waits for it, far more user visible. If 
this suggests tuning for acceptable write and max read speed, and 
setting the readahead higher than default, then you have reached the 
same conclusion as I did.

> I have a remote backup system configured (with rsnapshot), which does
> backups two times a day. So I'm not afraid to lose all my data due to
> disc failure. I want absolute speed.
>
> Currently I have Raid-0, because I was thinking that this one is
> fastest. But I also don't need twice the capacity. I could use Raid-1
> as well, if it was faster.
>
> Due to recent discussion about Raid-10,f2 I'm getting worried that
> Raid-0 is not the fastest solution, but instead a Raid-10,f2 is
> faster.
>
> So how really is it, which level gives maximum overall speed?
>
>
> I would like to make a benchmark, but currently, technically, I'm not
> able to. I'll be able to do it next month, and then - as a result of
> this discussion - I will switch to other level and post here
> benchmark results.
>
> How does overall performance change with the number of available drives?
>
> Perhaps Raid-0 is best for 2 drives, while Raid-10 is best for 3, 4
> and more drives?
>
>
> best regards
>   


-- 
Bill Davidsen <davidsen@tmr.com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark