> 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. 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? > Question: are you always swapping in a *new* disk each week or > re-inserting the disk from the previous week? It's a rotation, so re-inserting 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. Ugh. Thanks for your reponse.