At Wed, 16 Feb 2011 12:00:27 -0500 (EST) CentOS mailing list <centos@xxxxxxxxxx> wrote:
>
> We have about 50 CentOS servers with software RAID level 1 (mirroring).
> Each week, we swap out one of the drives (the one in the second of four
> hot-swap bays, only the first two of which contain drives) on each server
> and take them offsite for safekeeping.
>
> 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.
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.
Question: are you always swapping in a *new* disk each week or
re-inserting the disk from the previous week?
>
> It also confuses smartd, which AFAIK, needs the correct device names to
> report accurately.
>
> Ideally, we'd like to force the OS at some level to always see these
> devices as /dev/sda and /dev/sdb. If not, is there at least some way to
> configure smartd to be "smart" and recognize which devices are in use?
The cure might be that you need to do a reboot to properly rescan the
disks.
>
> TIA,
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>
--
Robert Heller -- 978-544-6933 / heller@xxxxxxxxxxxx
Deepwoods Software -- http://www.deepsoft.com/
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