Software RAID 0 HOW-TO

zpet731 · Posted: Thu Mar 31, 2005 7:29 am Post subject:

Hi everyone,

I am posting again to clarify a few things and ask a more general question.

I stated earlier that I have just built a:

AMD64 system 3200+
GA-N8NF-9 motherboard
6600 GT graphics card
1GB RAM
2 SATA 160GB drives

Now, Im only planning to run gentoo on this system so no dual boot or anything.

I've read quite a bit on SATA raid threads, most of the threads are excellent but I still need a few things answered before I start installing gentoo on it. Im using a minimal 2005.0 image that I downloaded off the net.

Now if I am to use Raid 0 setup what is my best option do I use the motherboard raid or not? Im not sure which way is better so hopefully someone can enlighten me on this issue.

Also if I am to use the software raid and control it completely from linux do I need to disable the raid in the bios? My motherboard asks me to setup the array each time I boot up and the sata raid is enabled by default. Can someone explain what needs to be done. Thanks!!!
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Phk · Posted: Thu Mar 31, 2005 10:40 am Post subject:

Use raid in the MOBO, and then use gen2dmraid-0.99a like i did to create an initrd.

It's simpler then having to define partitions by hand

See the thread i reffered above.
Any doubts, message me (here or there)

Good luck

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kamikaze04 · Posted: Fri Apr 01, 2005 5:09 pm Post subject:

I've two questions.

1)==================

I've noticed that if i put /dev/hda i get faster speeds than if i put only a partiton.
To test really the increase of the speed, what should i do?

Phk · Posted: Fri Apr 01, 2005 5:27 pm Post subject:

You should not be so paranoid about the speed measurement of your HDD..
Mounted or not; link partition or whole drive....

As long as it works...!

kamikaze04 · Posted: Fri Apr 01, 2005 5:34 pm Post subject:

As you can see, if i get only 4Mb/s (from 54 to 57) maybe it won't be relevant for me having RAID, but if I get 15Mb/s more(from 44 to 57), maybe yes.

There are another result more that is amazing from 28 to 57 = 29 Mb.

And the diference is only running hdparm with one parameter or other.

I only want to know how should i run it.
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kamikaze04 · Posted: Sat Apr 02, 2005 11:45 pm Post subject:

Okey, after few days doing some research and tests, this is what i've learned:

tip 1- It really matters if you have another disk as slave (sepeaking alwais about IDE devices).
As someone said in this thread, having attached a slave device makes accessing to the
master slower (in my case about 10Mb/s more). So try to have your hard disk alone in your bus.

tip 2- But what it really makes the difference is the location of your partitions. Before doing raid for whole disk, i've done raid with partitions of 1 o 2 Gb.

This is not only for RAID, it's for every partition in general. If the partiton is fisically first, it will be accessed faster (because of the speed of the disk is faster in the external zone than the internall zone)(at least for secuencial accesses)

That's why i've experienced that all the partitons located at the beginning are faster accessed.
So, if you really want to have a really faster RAID 0, you should raid two partitons like that.

tip 3- RAID 0 duplicates speed for reading and writing. But remember, it duplicates the velocity of the worst partition. So if you have a partition that has X Mb/s and another that has X+15Mb/s, when you raid them you will have 2*X and not 2*(X+15). So remember to choose well both partitions in both disks (said in tip 2)

tip 4- To ensure that the conditions of all your tests have the same conditions, before testing speed, do: "init 1"

Another thing i've concluded is that it really doesn't matter to hdparm mounted or not partitons.

=====

Now my results are:

FOR THE TWO PARTITONS USED IN THE RAID

/dev/hda2:

Timing buffered disk reads: 88 MB in 3.07 seconds = 49.1 MB/sec

/dev/sda3:

Timing buffered disk reads: 146 MB in 3.02 seconds = 55.7 MB/sec

FOR THE RAID

/dev/md/1:
Timing buffered disk reads: 172 MB in 3.01 seconds = 93.55[/b]MB/sec
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Phk · Posted: Sun Apr 03, 2005 6:09 pm Post subject:

Nice tips

Really HDD tunning

Thanks
_________________
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gnychis · Posted: Sat Apr 16, 2005 9:10 pm Post subject:

I followed this guide exactly, reboot my computer, it checks for discs in my cd-rom, then just freezes and doesn't go anywhere
(IC7-MAX3)

any ideas?

is it possible for me to go back into liveCD and remount my system to check everything?

Thanks!

snakernetb · n00b Joined: 27 Apr 2005 Posts: 2

I have a MSI board w/ the raid controller on MOBO. I really want to go w/ gentoo, for a learning experience and also due to the fact that it is highly configurable. I want to run a RAID 0, and notice that they have this link at the Promise website:

http://www.promise.com/support/download/download2_eng.asp?productId=9&category=driver&os=100&go=GO (Partial Linux source code)

I was unaware of this "software" option, but have been using linux in various flavors for years. Guess I didn't dig enough... But this is my first attempt at a raid0 setup so can you blame me? My main question is why not try to make this driver work? This all looks simple but are you really getting everything you can out of the onboard controller? Also noted as I looked through here that this is referred to as more of a driver driven raid controller, i.e. windows driver related. I am planning on using this system as my main system until I can get a 64bit system bought and built. Until then I want to wring all the performance I can out of it. From what I gather I just want to turn off the raid controller in the bios and address these disks as regular IDE in gentoo? Also noted something about IRQ interrupts. Has anyone ever gotten a driver option to work on the 2.6 kernel? Any info on this deal is appreciated. If not I will trying knocking the software option out. Thanks once again.

Muddy · Posted: Fri May 27, 2005 1:42 am Post subject:

so from the how-to I'm getting that your wasting space on one drive as you only put your boot partition on one and then you have this unused partition on the other??

BernieKe · Posted: Mon Dec 05, 2005 7:20 pm Post subject:

Hmmz

I'm getting hdparm results on my two (identical disks) at 40MB/s
and hdparm results on my raid 0 array (comprising those two disks) at 79MB/s

so far so good

but time cp VTS_01_1.VOB /home (timed copy of a 1gb file from another hd to the raid array)
gives 54secs, so only about 17MB/s
while the same copy takes only 50secs when I just mount one of the hd's...

these tests have been done with reiserfs, ext3 and ext2, with reiserfs and ext3 giving the same performance;
and ext2 average a little better
and I've tried with both a blocksize of 128 and 512, giving no difference what so ever

so I'm wondering: why is real-life performance so poor, and why is the array even slower than using a regular harddrive?

eae · Apprentice Joined: 28 Dec 2004 Posts: 211

Hmm I have a couple of questions (I haven't read the whole thread):
I have two hard disks which are currently on the same ide channel: one is master and the other is slave. I read somewhere that the optimal setup would be to have them on separate channels (both masters), is it true? The problem is that I have a dvd burner and a dvd reader too, and I heard that putting a them on the same channel as an hard disk slows down hard disk performance... So if I put both hard disks as master on the two ide channels and the dvd readers as slaves, will I improve or decrease performance? (and by the way, can I do that without destroying the raid 0 that i am currently using?)

By the way my hard disk speeds seem kinda bad :/