My question is in the title... here is some background:
[OS is Linux.]
[UPDATE: The contents of this RAID0 is redundant (sync'd from SCM). I am not worried about the increased risk of data loss.]
[UPDATE 2: Practically, I'm likely splitting hairs here. But in addition to trying to solve a practical problem, I'm wanting to improve/confirm my understanding of the theoretical.]
I have an automated build server that I use to compile the source code of a very large project, and I am looking to minimize my build times. I figure that the best possible build times will happen when the machine stays CPU-bound for the entire duration of the build (i.e., all cores loaded at 100%, the whole time.) This is of course an idealized goal that can only be approached asymptotically.
I can tell from the behavior of the build (mostly, watching the output of mpstat) that the greatest enemy of my goal is %iowait. There are times when I see a non-negligible %idle, and I consider that a modest failure of the kernel's scheduler, and/or small inefficiencies in Make's ability to parallelize the build. But this is generally not big enough for me to worry about. On the other hand, %iowait quite frequently gets seriously oversized... and my CPU load drops dramatically. I believe this usually happens when some threads are trying to link up (write) large libraries to the (software-controlled[*]) RAID0 while other threads are trying read source code.
(Please ignore for the moment the fact that I can move the output writes to a different volume & controller than the source code. That is planned.)
I am considering switching to SSDs. But in that case, I think it is probably best to abandon the software RAIDing[*] of the drives. My intuition is: the access times of the SSDs are so quick, and the transfer times so fast, that a simple LVM of 4 SSDs will squash my %iowaits to near-nothing, and my cores will then be constantly pegged, doing the maximum amount of useful work.
... In which case, software control of 4 RAIDed SSDs would needlessly increase my %sys, leaving less for %user. My cores would still be pegged, but there would be less "useful" work getting done.
Is my intuition on software-RAID0'ing SSDs correct, for this particular goal?
[*] BONUS QUESTION: There is a RAID controller on the motherboard, but my understanding is that it is just 'fake RAID', supplying volume management functions within the BIOS option ROM, but otherwise just software RAID. So I don't use it. But would a true hardware RAID controller even be helpful here? It is clear I can peg my cores quite easily on this machine; I just can't sustain it. I believe SSDs will mostly solve that stamina problem, and I find myself wondering if even a real hardware RAID controller can improve on that.
