[mythtv-users] RAID on Fedora Core 3?

[Blues Guy]

Max Waterman wrote:

> I'm having a problem creating my raid device.
>
> My first raid device is /dev/md0 and that works fine; but /dev/md1 
> doesn't exist.
>
> I can create it manually with :
>
> # mknod /dev/md1 b 9 1
> # mknod /dev/md2 b 9 2
> # mknod /dev/md3 b 9 3
> ... etc
>
> and reassemble and mount again, and all is well...but the /dev/mdX 
> files (apart from /dev/md0)
> disappear when I reboot.
>
> How do I stop them disappearing?
>
> Max.
>
Jumping into this conversation late, but better later than never maybe?  
I use an old 850Mhz PIII on an old IntelBX motheboard with a new(ish) 
Promise SATA150 TX4 (non-raid, i.e. cheap) card, and do software raid 
across four 250GB Seagate SATA (Dmesg says "Model: HDS722525VLSA80") 
with three PVR-250 encoders.  This box also acts as the NFS store for my 
mythvideo collection and my diskless frontend.  It holds up reasonably 
well, although it's slightly underpowered when it's doing a lot of 
commercial flagging.

I wanted to use all four disks as RAID5, but you can't boot from RAID5, 
and I also wanted LVM to be able to stretch the filesystem down the 
road...so my raid config ended up looking like this.. (as setup during 
FC2 install)

[root at atlas log]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/Volume00-LogVol01
                      9.7G  3.0G  6.3G  32% /
/dev/mapper/Volume00-LogVol02
                      150G   78G   73G  52% /mnt/exports
/dev/mapper/Volume00-LogVol03
                      537G  377G  160G  71% /mnt/store
/dev/md0               99M  9.8M   84M  11% /boot

The three logical volumes sit on top of  /dev/md1 and boot is obviously 
/dev/md0.

mdadm reports:

[root at atlas log]# mdadm -D /dev/md0
/dev/md0:
        Version : 00.90.01
  Creation Time : Wed Oct 20 00:50:16 2004
     Raid Level : raid1
     Array Size : 104192 (101.75 MiB 106.69 MB)
    Device Size : 104192 (101.75 MiB 106.69 MB)
   Raid Devices : 2
  Total Devices : 4
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sun Jan  2 12:23:55 2005
          State : clean, no-errors
 Active Devices : 2
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 2


    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1
       2       8       49       -1      spare   /dev/sdd1
       3       8       33       -1      spare   /dev/sdc1
           UUID : 2c8b5b5d:2a357a87:6f39ff28:fea0972d
         Events : 0.791

[root at atlas log]# mdadm -D /dev/md1
/dev/md1:
        Version : 00.90.01
  Creation Time : Wed Oct 20 00:43:38 2004
     Raid Level : raid5
     Array Size : 732274176 (698.35 GiB 749.85 GB)
    Device Size : 244091392 (232.78 GiB 249.95 GB)
   Raid Devices : 4
  Total Devices : 4
Preferred Minor : 1
    Persistence : Superblock is persistent

    Update Time : Sun Jan  2 06:13:14 2005
          State : dirty, no-errors
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-asymmetric
     Chunk Size : 256K

 Rebuild Status : 82% complete

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       8       18        1      active sync   /dev/sdb2
       2       8       34        2      active sync   /dev/sdc2
       3       8       50        3      active sync   /dev/sdd2
           UUID : 5ffc83ea:ead70b39:511cd279:86fd2eeb
         Events : 0.7539628

So you see /dev/md0 actually has two somewhat wasted hot-spares, but it 
keeps all the partition sizes in sync and makes it easier for me to 
manage.  Besides it's only a 100MB per drive which, in myth terms, is puny.

You can also see that my machine crashed earlier and the array is still 
resyncing. :-)  I blame the New Year's Twilight Zone marathon I 
recorded... it had been running fine for the last two months.

Don't know if this is useful, but there's my 2 cents...

Greg