failing drive Post: 302216787

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Operating Systems AIX failing drive Post 302216787 by bakunin on Monday 21st of July 2008 06:58:05 AM

07-21-2008

Registered User

How this is exactly done is depending on the RAID adapter (more precisely: the adapters driver software), so i can give you only general directions.

If the failing disk is part of a RAID you will probably not be able to manage the disk device itself. A RAID works like this: there are several disks connected to an adapter. The driver software of the adapter makes one big virtual disk out of the several physical ones and presents this virtual construct as a physical disk to the machine. (This is what is done during the "RAID initialization" or however it is called with your software. The driver/adapter writes some bookkeeping information onto the physical disk to be able to use them the described way.)

Only this virtual disk is added to a VG as a "Physical Volume" and from there on normal LVM procedures apply.

Your first task is to make the PV free from OS access. You can do this by either breaking the mirror (if the VG is mirrored) or by varying off the VG as zaxxon suggested. Since the "disk" in the VG is only a virtual construct there is no strict relationship between disks and logical volumes. All the logical volumes on the virtual RAID disk are "smudged across" the physical disks comprising the RAID.

After this you need to use the adapters driver software (in case of the IBM SCSI RAID adapter this is plugged into SMITty and the diag utility) to remove the disk from the RAID, after which the RAID is in status "reduced". then physically change the disks and add the new disk to the RAID. This will probably take some time as the new disk has to be written with the data first to be useful in the RAID. Only then varyon again and start using the VG again.

Do you need to backup? In principle you don't, because in a RAID all the disks hold all the information with redundancy. The classical case is 5 disks holding the capacity of 4 - for this penalty it is possible to replace every single disk without losing data, because the data it holds is also available on the other 4. This does NOT mean that a backup would be a bad idea: not at all! It is better to have a backup you don't need than to need a backup you don't have.

I hope this helps.

bakunin

bakunin

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LEARN ABOUT NETBSD

mlxctl

MLXCTL(8)						    BSD System Manager's Manual 						 MLXCTL(8)

NAME

     mlxctl -- Mylex DAC960 family management utility

SYNOPSIS

     mlxctl [-f dev] [-v] [-a] status [drive] [...]
     mlxctl [-f dev] [-a] detach [drive] [...]
     mlxctl [-f dev] [-a] check [drive] [...]
     mlxctl [-f dev] rebuild channel:target
     mlxctl [-f dev] cstatus
     mlxctl [-f dev] rescan
     mlxctl [-f dev] config

DESCRIPTION

     The mlxctl utility performs status monitoring and management functions for Mylex DAC960 RAID controllers and attached devices.

     The following options are available:

     -a       Apply the action to all drives attached to the controller.

     -f dev   Specify the control device to use.  The default is /dev/mlx0.

     -v       Increased verbosity.

     The following commands are available:

     cstatus  Display the controller's current status.

     status   Display the status of the specified drives.  This command returns 0 if all drives tested are online, 1 if one or more drives are
	      critical and 2 if one or more are offline.

     rescan   Re-scan the logical drive table, and attach or detach devices from the system as necessary.

     detach   Detach the specified drives.  Drives must be unmounted and unopened for this command to succeed.

     check    Initiate a consistency check and repair pass on a drive that provides redundancy (e.g., RAID1 or RAID5).	This command returns imme-
	      diately.	The status command can be used to monitor the progress of the check.

     rebuild  Rebuild onto the specified physical drive.  Note that there can be only one running rebuild operation per controller at any given
	      time.  This command returns immediately.	The cstatus command can be used to monitor the progress of the rebuild.

     config   Write the current system drive configuration to stdout.

EXAMPLES

     Display the status of drive ld3 attached to the controller mlx1:

	   mlxctl -f /dev/mlx1 -v status ld3

SEE ALSO

     ld(4), mlx(4)

HISTORY

     The mlxctl command first appeared in NetBSD 1.5.3, and was based on the mlxcontrol utility found in FreeBSD.

BUGS

     Modifying drive configuration is not yet supported.

     Some commands do not work with older firmware revisions.

     Error log extraction is not yet supported.

BSD
								  April 10, 2000							       BSD