[CentOS] Software RAID Level 1, smartd and changing dev numbers

Wed Feb 16 18:27:16 UTC 2011
yonatan pingle <yonatan.pingle at gmail.com>

partprobe as root should refresh the kernel partition / disk cache
instead of a reboot.


On Wed, Feb 16, 2011 at 7:30 PM, Robert Heller <heller at deepsoft.com> wrote:
> At Wed, 16 Feb 2011 12:00:27 -0500 (EST) CentOS mailing list <centos at centos.org> 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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>>
>>
>
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> Robert Heller             -- 978-544-6933 / heller at deepsoft.com
> Deepwoods Software        -- http://www.deepsoft.com/
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-- 
Best Regards,
Yonatan Pingle
RHCT | RHCSA | CCNA1