Kernel 2.6 MM sources software raid interesting findings....

[ravenqr]

Well to start I have an asus p4p800 with p4 2.66 533mhz overclocked to 3.02 ghz successfully..emerged world and system (bootstrapped) just fine overnight and no failures..

All this installed onto a software raid array made u of HALF of a SATA seagate barracude 7200.1 drive..and a WHOLE maxtor 7200rpm IDE drive....I never thought this would work but i was adventurous.

The reason I am posting this is becuase I have fiddled with software raid 0 here and there for a month now..and was never quite happy with the performance on the IDE drives...I would get like 80 mb/s but I knew I should have been getting more....

Anyways, the SATA drive by itself hdparms at 55 mb/s and the IDE drive at about 47 mb/s...

However, being that I had to unfortunately rebuild my entire system due to inconsistencies with GCC 3.4 and the current portage packages...i said what the hell and I tried this out.

No stability problems yet...but now using 40gb from a sata and a whole 40gb ide drive in sata raid 0 fresh install of gentoo, hdparm now yields me

111 mb/s

all the time. WOW! I was contemplating buying another sata drive to put them in software raid0 but i don't think it's necessary now. I can use the other half of the sata drive as a "backup" to transfer my existing system to now just in case i want to screw around with stuff again with unstable things in the future.....

However, I want to include a couple of pointers that I've learned with software raid0 through trial and error, mostly ERROR:

If you are using two different drives for software raid (two different sizes, or in my case, even two different drives with two different interfaces), the sizes of the partitions are important. For example,

My SATA is 80 gb.
My IDE is 40 GB.

However, this translates into something like the IDE being 41111 mb and the sata being 79818 mb. Not quite even right?/

So, to make my 80 gb raid0 setup, I had to waste a lil bit of the my ide drive because it is smaller.

When I was making the partition on the IDE drive...(it is 41111 mb total) I simply made the partition size typed as "39000" so I could be close enough to the end of the drive's capacity but not to close that I would risk the partitions on both being unequal. Typing "39000" rounded it off to like 38898 or something....

Now then I cfdisk'd on the SATA drive and made a partition by typing "39000" and it rounded it off to the same size of 38898...now I have two EQUAL partitions to melt into a software raid0.

Believe me, if you have never done this before, you WANT YOUR PARTITION SIZES EQUAL.
By typing in these amounts exactly on each (and wasting just a bit of my ide drive) I had ensured that the sizes were exactly equal and that the raid array would work as expected. This can be verified for you by taking a look at the output of dmesg and look at where it compares sdax to hdbx or whatever your case may be.

In any event, you should see a big "EQUAL!" while examining this output...

Software raid0 is a great way to increase your performance drastically....

Hope these tips help somebody in their adventures to gain that extra performance from their existing hardware....

Peace

[PrakashP]

Just out of interest: Could you do a cat /dev/mdX>/dev/null and watch gkrellm2 hd read speed. still >110MB/s?

[ravenqr]

Yes gkrelmm2 yields approximately 92-114 consistently

[prbox]