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

["Keld Jørn Simonsen" <keld@dkuug.dk>]

On Wed, Jan 30, 2008 at 07:21:33PM +0100, 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...
> 
> 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?

Teoretically, raid0 and raid10,f2 should be the same for reading, given the
same size of the md partition, etc. For writing, raid10,f2 should be half the speed of
raid0. This should go both for sequential and random read/writes.
But I would like to have real test numbers. 

best regards
keld