RE: Raid Failed What to to

["Dominik Sennfelder" <Sennfelder@gmx.de>]

Hello

Thanks for your help.
I created the array with mkraid /dev/md0 after i added the entrys in
/etc/raidtab.
I analyzed the logs an saw that one disk failed one day before,
so the raid run with 3 discs. My fault was to raidsetfault the wrong drive.
But in that moment the Raid broke up an no write was possilble because it
got remountet -ro. After i hotadded it again, it tried to sync but with only
two discs syncing wouldn't be possible. The drive i removed wan't really
faulty, it was just set faulty. I even could browse the filesystem when just
2 discs run. 
So can i reassamble the drive mith mdadm? or do i have to use mkraid?

Thanks for your help and suggestions.

Dominik


> This is an example for using mdadm where the second of three disks is bad.
> But you must use the same chunk size and other RAID5 parameters or the
> array
> will have bogus data.  It would be nice if you still have the original
> command you used to create the array.
> 
> mdadm -C /dev/md0 -l 5 -n 3 /dev/hda3 missing /dev/hdc3
> 
> Guy
> 
> -----Original Message-----
> From: Guy [mailto:bugzilla@watkins-home.com] 
> Sent: Friday, May 21, 2004 10:00 AM
> To: 'Clemens Schwaighofer'; 'Dominik Sennfelder'
> Cc: 'linux-raid@vger.kernel.org'
> Subject: RE: Raid Failed What to to
> 
> If you re-make the array with the same parameters as it has now the data
> will not be lost (assuming it is still there now).  If 1 disk is really
> bad
> then leave it out.
> 
> The procedures depend on which program you use to create the array.  Do
> you
> use mkraid or mdadm?
> 
> Guy
> 
> -----Original Message-----
> From: linux-raid-owner@vger.kernel.org
> [mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Clemens
> Schwaighofer
> Sent: Friday, May 21, 2004 4:45 AM
> To: Dominik Sennfelder
> Cc: linux-raid@vger.kernel.org
> Subject: Re: Raid Failed What to to
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Dominik Sennfelder wrote:
> | Hello
> |
> | I have got a Raid 5 with 4 160 GB Disk,
> | On of the Disks Failed because. But I know its OK I had this for some
> | times.
> | A Restart solved The Problem.
> | But now  Tried to raidhotremove the Drive and removed the wrong drive.
> | I just recongized the Problem after i raidhotadded itagain.
> | No the Raid tries to sync again.
> 
> well if you removed two drives from your Raid5 array, it might got
> competly out of sync and then there is no way to recover. I have never
> tried this with my raid, but if you add another disk it well be
> re-synced, ergo it tries to rebuild the array out of the CRCs on the
> other drives, if you remove two, you don't have enough redudant data to
> do this (raid 6 can recover from a 2 drive failure).
> 
> I hope you have a backup.
> 
> - --
> Clemens Schwaighofer - IT Engineer & System Administration
> ==========================================================
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> ==========================================================
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-- 
Mfg Dominik Sennfelder
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