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replacing a specific drive in a RAID 1 set

Posted on 2008-06-24
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Last Modified: 2012-06-27
We have a dell 1600SC with a Perc4/DC controller (hot swappable).  The operating system is on a pair of raided (level 1)73GB scsi drives, the data is kept on a set of 3 Raided (level 5) 148 gb scsi drives.  We use one 148 gb drive as the global hot spare.

One of the 73gb drives failed, the perc4 card appropriately brought in the 148gb drive to the raid1 set.  Now I have a replacement 73gb hard drive.  Through Dell Open Manage 5.4 (while the server is running) I want to split the mirror, return the 148 gb hard drive to global spare status, and remirror using a new 73gb drive I own.

I'd like to know in advance what to expect from the reconfigure | split mirror path on Open Manage.

1.  Will I be able to tell Open Manage which hard drive I want to remove from the mirror when I split the mirror.

2.  I will then insert the new 73gb hd into the hot-swap slot.  Will I be able to remirror without taking the server down?

3.  I assume I will then be able to re-assign the 148gb drive to global spare, again.

Thanks in advance.
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Question by:dakota5
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scrathcyboy earned 250 total points
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If you had a RAID set for 73GB, then even though you added a 148GB drive to replace the dead one, that drive should still only be formatted to the original 73GB RAID capacity.  Therefore you should be able to remove it, and insert a new 73GB drive with no problems.  However, before you do this, read the PERC controller specifications.  Each RAID controller does its own thing, many default to trashing a raid upon any changes -- so be certain before you do it.
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by:dakota5
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The Perc controller specs are not clear on these points, especially when actions are performed within the Dell Open Manage system.  I was hoping to hear from someone with specific experience with this Perc controller.
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by:scrathcyboy
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my input was relevant to your question, was it not?  No RAID documentation touches on the thorny issues of what happens when their RAID fails, and can it be migrated or not to another RAID, and if so, how.  They all avoid CRUCIAL issues with RAID controllers.  Only if you assume the worst are you potentially safe.
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by:dakota5
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By experimenting during off hours, today, we established the following.
for Perc4 using Dell OpenManage Server Administrator to make these changes while the Server is running (i.e., not when rebooted into the Perc configuration setup in bios)

1.  go to Perc4 physical disks.  Take the physical disk that you want to replace "offline".  This degrades the RAID set and the audible alarm will start to beep.

2. go to Perc4 virtual disks.  Assign/unassign dedicated hot spare.  Assign the new disk that you want to be in the raid set.  Once assigned, the controller will automatically start the bebuild of the set.

3.  go back to physical disks.  Assign the disk that you want to be the global hot spare.

This process is not documented in the Dell OpenManage Help.  And split mirror and unmirror are not supported for the Perc 3,4,5 or 6 controllers (see appendix in the OpenManage help).
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