On Wed, 16 Feb 2011, James Smallacombe wrote:
To: CentOS mailing list centos@centos.org From: James Smallacombe james@sicom.com Subject: Re: [CentOS] Software RAID Level 1, smartd and changing dev numbers
At Wed, 16 Feb 2011 12:00:27 -0500 (EST) CentOS mailing list centos@centos.org wrote:
The problem is, the kernel seemingly randomly switches between /dev/sdb and /dev/sdc for these devices. This makes the process slower by requiring more manual input where a script(s) could otherwise suffice.
I'm assuming these are actually SATA disks with a controller that supports hot-swap.
Correct.
What I think is happening is that the kernel retains some 'memory' of the pulled drive (say /dev/sdb) and when the fresh drive is installed, a new dev file is created (/dev/sdc). Eventually, /dev/sdb is forgotten by the time the next 'swap' and /dev/sdb is assigned to the next fresh disk.
Interesting...one would think that this behavior would be consistent across all servers then, but it isn't. Most accept the same dev, /dev/sdb, but some assign /dev/sdc. Is there a way to just disable /dev/sdc and force the kernel to use /dev/sdb every time?
Can you identify any differences in the machines that don't re-assign the dev files, and the machines that do?
Is this anything to do with UUID's on the drives/partitions?
What parts do you have on the RAID drives?
How are the drives setup as RAID - as bare drives/partitions, or via LVG?
Keith
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