Re: software raid drive failed, please provide step bu steptorebuild

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Ok I totally see your point about striping my swap partition.
I read it some howto a few years back.

I did just what you said
I paritioned my new drive the exact same as the other two.
I issued the command
mdadm /dev/md2 -a /dev/sdc3
and the raid  md2 is rebuilding as I write this.

So how do I get setup my swap as you described?
Now I have three drives w/ partition
265072 sda2
265072 sdb2
265072 sdc2

Thank you soooo much
Its 100 degrees, its Friday and now I have go outside and mow my lawn.
Look forward to reading your reply while sipping a cold one!


----- Original Message ----- From: "Jeff Vian" <jvian10@xxxxxxxxxxx>
To: "For users of Fedora Core releases" <fedora-list@xxxxxxxxxx>
Sent: Friday, July 28, 2006 6:48 PM
Subject: Re: software raid drive failed, please provide step bu steptorebuild


On Fri, 2006-07-28 at 18:03 -0500, Dan Carl wrote:
I know its a raid 0 is a stripe.
Its my swap partition.
Why would I need fault tolerance on my swap.

From your first post below:
       Now I can reach the drive via fdisk but I have made more
       problems now (no swap now)
       and I'm not sure the steps to rebuild.
That is a good reason to make sure that vital disk partitions are not
made critically weak.  When striping across 3 drives the failure
probability is made 3X as likely and any single failure toasts the
entire device.

Since swap can use multiple partitions the likelyhood of failure and
total loss of swap space can be reduced by simply defining multiple swap
partitions without using striping.



Anyway,
I did what Sam suggested.
md0 is fine, md1 doesn't exist
mdadm -Q -D /dev/md2
it yeilded
/dev/md2:
        Version : 00.90.01
  Creation Time : Mon Feb 14 06:42:28 2005
     Raid Level : raid5
     Array Size : 34812416 (33.20 GiB 35.65 GB)
    Device Size : 17406208 (16.60 GiB 17.82 GB)
   Raid Devices : 3
  Total Devices : 2
Preferred Minor : 2
    Persistence : Superblock is persistent
Update Time : Fri Jul 28 17:56:25 2006
          State : clean, degraded
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
Layout : left-symmetric
     Chunk Size : 256K
 Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       1       8       19        1      active sync   /dev/sdb3
       2       0        0       -1      removed
           UUID : b4b161bc:2953b117:9c13c568:47693baa
         Events : 0.31307539

So mdadm -a needs to be used to add the 3rd device back to md2.  Sam's
instructions were clear on that.  For more information and education use
the man page for mdadm.


MANAGE MODE
      Usage: mdadm device options... devices...
      This usage will allow individual devices in  an  array  to  be
failed,
      removed  or  added.  It is possible to perform multiple
operations with
      one command. For example:
        mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1
      will firstly mark /dev/hda1 as faulty in /dev/md0 and will then
remove
      it  from the array and finally add it back in as a spare.
However only
      one md array can be affected by a single command.


I would do the following that you have not already stated done.
1. create the partition(s) on your new /dev/hdc
2. use mdadm as follows to add it to md2
    mdadm /dev/md2 -a /dev/sdc3
note that I assume your partitions are created and numbered as you have
already stated.

What if the  next step this is my mail server and I really don't have the
time to reload it.
I have my fstab, partition, mdstat,  infomation.
I ran this command sfdisk -d > sdb-parts.dump before a added the new drive.
Will any of this help?

fdisk -l will list the partition information for each drive including
start and end cylinders such as this.

       [root@raptor pgsql]# fdisk -l /dev/hda

       Disk /dev/hda: 250.0 GB, 250059350016 bytes
       255 heads, 63 sectors/track, 30401 cylinders
       Units = cylinders of 16065 * 512 = 8225280 bytes

          Device Boot      Start         End      Blocks   Id  System
       /dev/hda1   *           1          21      168651   83  Linux
       /dev/hda2              22         532     4104607+  83  Linux
       /dev/hda3             533         721     1518142+  82  Linux
       swap
       /dev/hda4             722       30401   238404600    5  Extended
       /dev/hda5             722        1359     5124703+  83  Linux
       ....

From that you can get not only the size of each partition, but the
actual cylinders used and can recreate the table on the new drive
appropriately with fdisk.


Like I said before the only raid/partition experience I have is at initial
installation.



----- Original Message ----- From: "Jeff Vian" <jvian10@xxxxxxxxxxx>
To: "For users of Fedora Core releases" <fedora-list@xxxxxxxxxx>
Sent: Friday, July 28, 2006 5:44 PM
Subject: Re: software raid drive failed, please provide step bu step
torebuild


> On Fri, 2006-07-28 at 16:29 -0500, Dan Carl wrote:
> > I have/had a software raid running and sdc drive failed.
> > I got a replacement drive today and installed it.
> > My only experience with set partitions and raids in during initail
setup.
> > I could not fdisk the new drive because i guess it wasn't reconized > > so I
> > rebooted.
> > Now I can reach the drive via fdisk but I have made more problems now
(no
> > swap now)
> > and I'm not sure the steps to rebuild.
> > Background:
> > I have a FC3 with a software raid.
> > I have 3 SCSI 18gb hard drives
> > If I recall this how I set it up
> > md0 /boot 100MB raid 1 sda, sdb and sdc as spare
> > md1 /swp 768MB raid 0 sda, sdb, sdc
> This toasted your /swp partition.
> Raid 0 is striping, and a single failure toasts the entire device.
>
> You would have been ahead with a non-raid swap, and had 3 separate
> partitions, one on each device, for swap. Failure of one would not > have
> toasted all.
>
>
> > md2 / ext3 33GB raid 5 sda, sdb, sdc
> >
> > Can someone please help?
> >
>
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