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Valin
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PostPosted: Thu Dec 09, 2004 6:40 pm    Post subject: Reply with quote

I've setup a 3 drive RAID 0, but Grub refuses to setup.

/boot = /dev/md0
swap = /dev/sda2, /dev/sdb2, /dev/sdc2
/ = /dev/md1

Additionally, the instrustions at the beginning of this topic forget to mention you have to first create the md devices in /dev before you can run mkraid.

The problem I'm getting is that Grub refuses to recognize hd0 to install itself into on the MBR. Can I get around this by installing to the boot partition instead? Even if I try it still whines about not finding anything about my drives in the BIOS...huh?
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Arainach
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PostPosted: Fri Dec 17, 2004 9:38 pm    Post subject: Reply with quote

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icn
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PostPosted: Mon Jan 31, 2005 11:51 pm    Post subject: Reply with quote

Is one single 36GB Raptor faster than 2 60GB SATA drives in RAID0? Also is it easy to have both Windows and Gentoo on the same drive with RAID 0 and which one do you install first if its possible? Any help would be appreciated. Thanks.
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R!tman
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PostPosted: Thu Mar 10, 2005 12:07 pm    Post subject: Reply with quote

I have serious performance problems on my new pc. I set up reiserfs on a raid 5 on 4 sata disks with a chunk size of 64K (mdadm standart). But compared to my old pc with only 1 ata disk (and reiser4) the raid performance is horrible.

My old system:
Code:
# time cat /scratch/big.file > /dev/null

real    0m49.614s
user    0m0.053s
sys     0m7.746s
# du -h /scratch/bigfile
2.2G    /scratch/big.file

My new system:
Code:
# time cat /scratch/big.file > /dev/null

real    0m55.600s
user    0m0.012s
sys     0m4.471s
# du -h /scratch/bigfile
2.2G    /scratch/big.file

Even a single sata drive should be faster than the rather old ata drive. The raid 5 is way too slow in my opinion.

What is really strange though is that:

Old system
Code:
# iozone -s 4096
        Iozone: Performance Test of File I/O
                Version $Revision: 3.226 $
                Compiled for 64 bit mode.
                Compiled for 32 bit mode.
                Build: linux

        Contributors:William Norcott, Don Capps, Isom Crawford, Kirby Collins
                     Al Slater, Scott Rhine, Mike Wisner, Ken Goss
                     Steve Landherr, Brad Smith, Mark Kelly, Dr. Alain CYR,
                     Randy Dunlap, Mark Montague, Dan Million,
                     Jean-Marc Zucconi, Jeff Blomberg,
                     Erik Habbinga, Kris Strecker.

        Run began: Thu Mar 10 12:43:36 2005

        File size set to 4096 KB
        Command line used: iozone -s 4096
        Output is in Kbytes/sec
        Time Resolution = 0.000001 seconds.
        Processor cache size set to 1024 Kbytes.
        Processor cache line size set to 32 bytes.
        File stride size set to 17 * record size.
                                                            random  random    bkwd  record  stride                                   
              KB  reclen   write rewrite    read    reread    read   write    read rewrite    read   fwrite frewrite   fread 
freread
            4096       4  104049  314064   512255   486165  397089  266838  392078  385437  394798   278637   286135  468387   
451354

iozone test complete.

New system
Code:
# iozone -s 4096
        Iozone: Performance Test of File I/O
                Version $Revision: 3.226 $
                Compiled for 64 bit mode.
                Build: linux-AMD64

        Contributors:William Norcott, Don Capps, Isom Crawford, Kirby Collins
                     Al Slater, Scott Rhine, Mike Wisner, Ken Goss
                     Steve Landherr, Brad Smith, Mark Kelly, Dr. Alain CYR,
                     Randy Dunlap, Mark Montague, Dan Million,
                     Jean-Marc Zucconi, Jeff Blomberg,
                     Erik Habbinga, Kris Strecker.

        Run began: Thu Mar 10 12:27:55 2005

        File size set to 4096 KB
        Command line used: iozone -s 4096
        Output is in Kbytes/sec
        Time Resolution = 0.000001 seconds.
        Processor cache size set to 1024 Kbytes.
        Processor cache line size set to 32 bytes.
        File stride size set to 17 * record size.
                                                            random  random    bkwd  record  stride                     
             
              KB  reclen   write rewrite    read    reread    read   write    read rewrite    read   fwrite frewrite   
fread  freread
            4096       4  323947 1037443  2026691  2119975 2020731 1160033 1967279 1410868 1952300   297132   985321 15
76018  2020731

iozone test complete.

Here it seems as the raid would indeed be quite faster. Strange...
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fatalglitch
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PostPosted: Mon Mar 14, 2005 10:00 pm    Post subject: Reply with quote

I haven't read through this whole post, so I apologize if I am repeating, but....

It should be noted, with software raid, there is one thing many people forget about, but is HUGE when is comes to both speed AND redudancy

- Each physical drive should be on a SEPERATE ide bus.

Ok, now I will explain this...
Performance - if both drives are on the same IDE bus....your really not gaining any speed increase by RAID0 (striping) due to the fact that the bus still has a maximum thoroughput, and will not exceed that amount...

Redundancy - this should be obvious. Yes hard drive's do go bad....but what happens when the bus goes bad? This may not be necessary for a desktop system, but for a server setup....this is MAJOR. Bus goes dead, then both your physical drives are gone....and the server crashes.

Just some FYI...

-Tom
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fatalglitch
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PostPosted: Mon Mar 14, 2005 10:03 pm    Post subject: Reply with quote

RAID0 will not stripe across 3 drives...your setup (if using software RAID) would be using 2 physical drives to stripe, and a backup drive...(which would be pointless).

If you have 3 drives, your better off using RAID5, as it gives the benefits of RAID0 as well as the redudancy of RAID1

Check your /etc/raidtab for your setup....

Tom

Valin wrote:
I've setup a 3 drive RAID 0, but Grub refuses to setup.

/boot = /dev/md0
swap = /dev/sda2, /dev/sdb2, /dev/sdc2
/ = /dev/md1

Additionally, the instrustions at the beginning of this topic forget to mention you have to first create the md devices in /dev before you can run mkraid.

The problem I'm getting is that Grub refuses to recognize hd0 to install itself into on the MBR. Can I get around this by installing to the boot partition instead? Even if I try it still whines about not finding anything about my drives in the BIOS...huh?
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fatalglitch
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PostPosted: Mon Mar 14, 2005 10:06 pm    Post subject: Reply with quote

Try doing a simulated hotswap of one of the partitions....software raid will sync both disks based on the most current times in the files.

Hotswapping (simulated!!! do NOT try to do a REAL IDE HOTSWAP) will resync the drives and should remove the "dirty" error.

-Tom

BlackB1rd wrote:
And my problem extends since it's not only the dirty status it returns. It also doesn't seem to update the 'Update time', which is very concerning. I guess that means is doesn't keep the RAID array synchronized? :(
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dioxmat
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PostPosted: Mon Mar 14, 2005 10:30 pm    Post subject: Reply with quote

FWIW, raid 5 software sucks. See this blog entry for some explanations on the subject.
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PostPosted: Tue Apr 05, 2005 4:39 pm    Post subject: Reply with quote

dioxmat wrote:
FWIW, raid 5 software sucks. See this blog entry for some explanations on the subject.

i couldn't more agree. i just threw away my partitions and am setting up a raid0 system
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Last edited by BlinkEye on Tue Apr 12, 2005 6:55 pm; edited 1 time in total
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neo_phani
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PostPosted: Tue Apr 12, 2005 6:44 pm    Post subject: Reply with quote

ok i tried this with 2 SATA drives and everything went but when i boot on the new kernel


checking root file system ...
ext2fs_check_if_mount: No such file or directory while determining whether /dev/md2 is mounted
fsck.ext3:NO such file


what could i have done wrong ? How do i fix this without having to do it all over again

Also i noticed i had a xfs in my /etc/fstab for md3 which should be ext3 instead ......please tell me how i can change this ? Can i use the boot cd and mount the /dev/md2 and edit stuff...i am lost

/dev/md0 /boot ext2 noauto,noatime 1 2
/dev/md2 / ext3 noatime 0 1
/dev/hda2 none swap sw,pri=0 0 0
/dev/hdc2 none swap sw,pri=0 0 0
/dev/md3 /home xfs noatime 0 1
/dev/cdroms /cdrom0 /mnt/cdrom iso9660 noauto,ro 0 0
proc /proc proc defaults 0 0
















my /etc/raidtab

# /boot (RAID 1)
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
chunk-size 32
persistent-superblock 1
device /dev/sda1
raid-disk 0
device /dev/sdc1
raid-disk 1
# / (RAID 1)
raiddev /dev/md2
raid-level 1
nr-raid-disks 2
chunk-size 32
persistent-superblock 1
device /dev/sda3
raid-disk 0
device /dev/sdc3
raid-disk 1
# /home (RAID 1)
raiddev /dev/md3
raid-level 1
nr-raid-disks 2
chunk-size 32
persistent-superblock 1
device /dev/sda4
raid-disk 0
device /dev/sdc4
raid-disk 1
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shakti
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PostPosted: Mon Apr 25, 2005 8:10 pm    Post subject: cannot determine md version: no MD device file in /dev Reply with quote

If you get this error create a script and run it...
Code:
for i in 0 1 2 3 4 5 6 7 8 9 10;

do mknod /dev/md$i b 9 $i;

done

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sro
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PostPosted: Tue May 03, 2005 7:32 am    Post subject: Reply with quote

This HowTo didn't work for me :?

my setup:

/dev/md0 = /boot, RAID1
/dev/md1 = /, RAID1
/dev/sda2, /dev/sdb2 = SWAP, no RAID

SATA Software Raid, Onboard SATA Controller, using module SATA_NV (compiled into the kernel).

when trying to boot, i'm receiving this error:

Quote:

ext2fs_check_if_mount: No such file or directory while determining wether /dev/md1 is mounted.
fsck.ext3: No such file or directory while trying to open /dev/md1

/dev/md1:
The superblock could not be read or does not describe a correct ext2 filesystem.


devfs=nomount gentoo=udev is set in my grub.conf

The /dev/md0 and /dev/md1 device nodes are successfully created by 'md' while booting, but when it's time for the kernel to access root, i'm getting an error as quoted above.

/etc/fstab is correct, the line for /dev/md1 says "ext3".

I'm working on this problem the last 7 days, but can't get my software raid1 booting...
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BlinkEye
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PostPosted: Tue May 03, 2005 8:10 am    Post subject: Reply with quote

chroot back and create a kernel with devfs support (do NOT activate "Automount at boot" though). after that boot your system with the following kernel options
Code:
gentoo=noudev

i had the same problems. this is udev :twisted:
after a succesfull boot with devfs you may switch back to udev - it will work.
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sro
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PostPosted: Tue May 03, 2005 9:18 am    Post subject: Reply with quote

Its working!

I followed your steps - udev is causing this problems.
With devfs support, the system now boots perfectly.

Thank you.
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dac
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PostPosted: Tue May 03, 2005 2:26 pm    Post subject: Cannot determine md version: no MD device file in /dev Reply with quote

I am new and just learning. Thererfore, I was following the directions when I ran into a problem.
Motherboard is ASUS A8V
I have setup two SATA drives using fdisk.
I run modprobe md
I create my raidtab file. I want to have Raid 1.

# / (RAID 1)
raiddev /dev/md2
raid-level 1
nr-raid-disks 2
chunk-size 32
persistent-superblock 1
device /dev/sda3
raid-disk 0
device /dev/sdb3
raid-disk 1


and then when I run "mkraid /dev/md*" , I get "Cannot determine md version: no MD device file /dev"
Why?
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sro
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PostPosted: Tue May 03, 2005 3:45 pm    Post subject: Reply with quote

running "mkraid /dev/md*" means, you should run "mkraid" for each of your arrays.

example for your RAID1:
mkraid /dev/md2
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BlinkEye
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PostPosted: Tue May 03, 2005 4:05 pm    Post subject: Reply with quote

if this doesn't solve your problem you use udev and MUST do the following:
Code:
cd /dev
MAKEDEV md

after that, try
Code:
mkraid /dev/md*

again
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dac
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PostPosted: Tue May 03, 2005 6:25 pm    Post subject: Reply with quote

I think that help because it is now syncing. Thanks.
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PostPosted: Mon May 23, 2005 12:44 pm    Post subject: Reply with quote

i followed the instructions but now when i tryed to do:

mkraid /dev/md0

i got:

Code:
cannot determine md version: no MD device file in /dev


ive alread modprobed md


also can I start md# with 1? 0 looks confusing :p
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BlinkEye
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PostPosted: Mon May 23, 2005 6:26 pm    Post subject: Reply with quote

how about reading my post second last from your post?
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PostPosted: Tue Jun 21, 2005 3:44 pm    Post subject: mkraid /dev/md0 says 'cannot determine md version: 6.' Reply with quote

I am installing Gentoo 2005.0 over top of my Redhat installation. I copied my /etc/raidtab from my old partition. I ran MAKEDEV md and then mkraid.

mkraid /dev/md0 says "cannot determine md version: 6."

I have tried with and without the boot option DOSCSI.

I read somewhere that someone had a problem with the same output, and ended up fixing it by recompiling without RAID 6.

Is there anything I can do to get this to work? Here is my old raidtab:

Code:
raiddev             /dev/md0
raid-level                  1
nr-raid-disks               2
chunk-size                  64k
persistent-superblock       1
nr-spare-disks              0
    device          /dev/sda5
    raid-disk     0
    device          /dev/sdb5
    raid-disk     1
... ommitted for brevity...
 
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fast40x
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PostPosted: Tue Jun 21, 2005 4:35 pm    Post subject: Reply with quote

I think I have my problem solved.

The first thing I did to start getting me on the right track is:

Code:
modprobe md


It was in the instructions, but I missed it.


then I realized I shouldn't be doing the mkraid in the first place, but rather:

Code:
raidstart


after that, mounting the systems was a breeze.
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PostPosted: Thu Jun 30, 2005 12:54 am    Post subject: New Tips Reply with quote

since this post hasnt been touched in a while I tried using the instructions in the first post with no success.
Here are my steps that did work.

I did everything in the first post except when it says to edit menu.lst you should really edit grub.conf.
When it came to running grub to install the boot loader i had errors. I found a bug report on another site
that helped me. you have to edit /etc/mtab to reflect the actual real physical drive and partition that will
hold the grub stage1. my /etc/mtab stated-->

/dev/md0 /boot *****

I changed it to-->

/dev/hda1 /boot ****

(the stars represent the part of the line I did not change)

this allowed me to run grub-install. I also changed /dev/hda1 to /dev/hdc1 and ran grub-install again
so both drives will have the boot loader. I am hoping this will allow me to still boot if the first drive fails.



Here is the original page with the bug report.
https://bugzilla.redhat.com/bugzilla/long_list.cgi?buglist=138572
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PostPosted: Wed Jul 13, 2005 5:46 pm    Post subject: Reply with quote

Got a question for y'all. I am about to get a new server. It has 4 SCSI 9.1G HDD's right now. Later on I am going to add 18.2G. I was wondering 2 things. One, can I swap out the 4 drives and replace them with 6 new ones? I know if I swap out 1 at a time it should rebuild the RAID, right? Also, could you look at what I think the config should be for the 4 drives.

Code:

-------------cfdisk

sda1   512   /boot   RAID 1
sda2   200M   /   RAID 5
sda3   3G   /var   RAID 5
sda5   3G   /home   RAID 5
sda6   500M   /tmp   RAID 5
sda7   *   /usr   RAID 5


sdb1   512   /boot   RAID 1
sdb2   200M   /   RAID 5
sdb3   3G   /var   RAID 5
sdb5   3G   /home   RAID 5
sdb6   500M   /tmp   RAID 5
sdb7   *   /usr   RAID 5

sdc1   512   swap   NO RAID
sdc2   200M   /   RAID 5
sdc3   3G   /var   RAID 5
sdc5   3G   /home   RAID 5
sdc6   500M   /tmp   RAID 5
sdc7   *   /usr   RAID 5

sdd1   512   swap   NO RAID
sdd2   200M   /   RAID 5
sdd3   3G   /var   RAID 5
sdd5   3G   /home   RAID 5
sdd6   500M   /tmp   RAID 5
sdd7   *   /usr   RAID 5


-------------- /etc/raidtab

# /boot (RAID 1)
raiddev                 /dev/md0
raid-level              1
nr-raid-disks           2
chunk-size              32
persistent-superblock   1
device                  /dev/sda1
   raid-disk               0
device                  /dev/sdb1
   raid-disk               1


# / (RAID 5)
raiddev    /dev/md1
raid-level 5
nr-raid-disks 4
persistent-superblock 1
chunk-size 32
parity-algorithm right-symmetric
device /dev/sda2
   raid-disk 0
device /dev/sdb2
   raid-disk 1
device /dev/sdc2
   raid-disk 2
device /dev/sdd2
   raid-disk 3


# /var (RAID 5)
raiddev    /dev/md2
raid-level 5
nr-raid-disks 4
persistent-superblock 1
chunk-size 32
parity-algorithm right-symmetric
device /dev/sda3
   raid-disk 0
device /dev/sdb3
   raid-disk 1
device /dev/sdc3
   raid-disk 2
device /dev/sdd3
   raid-disk 3

# /home (RAID 5)
raiddev    /dev/md3
raid-level 5
nr-raid-disks 4
persistent-superblock 1
chunk-size 32
parity-algorithm right-symmetric
device /dev/sda5
   raid-disk 0
device /dev/sdb5
   raid-disk 1
device /dev/sdc5
   raid-disk 2
device /dev/sdd5
   raid-disk 3

# /tmp (RAID 5)
raiddev    /dev/md4
raid-level 5
nr-raid-disks 4
persistent-superblock 1
chunk-size 32
parity-algorithm right-symmetric
device /dev/sda6
   raid-disk 0
device /dev/sdb6
   raid-disk 1
device /dev/sdc6
   raid-disk 2
device /dev/sdd6
   raid-disk 3

# /usr (RAID 5)
raiddev    /dev/md5
raid-level 5
nr-raid-disks 4
persistent-superblock 1
chunk-size 32
parity-algorithm right-symmetric
device /dev/sda7
   raid-disk 0
device /dev/sdb7
   raid-disk 1
device /dev/sdc7
   raid-disk 2
device /dev/sdd7
   raid-disk 3


I am guessing I can just add on the other 2 drives later on when I get them. Also, is it posible to do LVM on top of this? If so, how would I do it? Thanks a lot.
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PostPosted: Wed Sep 28, 2005 1:58 pm    Post subject: root partition Reply with quote

I have followed this how-to word for word and everything has gone smoothly, until it came to rebooting into the new kernel.

I have setup grub on a mirrored boot partition which is found and the kernel loads, but upon loading the striped root partition a kernel panic occurs where it cannot open root device "md2".

kernel support is built in for raid mirrored and striped and so is reiserfs (my only file system type).

Running 2.6 kernel.

The striped raid volume works on the livecd after appropriate MAKEDEV modprove md and mkraid and can be accessed after mounting, so it looks like a kernel problem although I can't think what I am missing.

Any ideas?

Thanks.
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