On 02/18/2013 11:06 PM, Nico Kadel-Garcia wrote:
> IDE drives used to  be listed as "/dev/ide0, /dev/ide1, etc." in
> deterministic fashion, but that got tossed out when they started
> labeling all drives as /dev/sda to gove access to special SCSI
> compatible commands.....

Aka 'the libata takeover'.  It does make all drives pretty much 
consistent.  There are still a few older controllers that behave better 
with the old IDE drivers than with libata; old Intel P4 chipsets in 
particular.

> The result is that it's guesswork. This is why our favorite upstream
> vendor tried for a while to use "LABEL=" settings to identify
> particular partitions, instead of trying to deduce what would be
> detected where.
>

This is partially due in EL6 to the use of dracut and it's new initrd 
udev-ish system.  I have one RHEL 6 box that is hooked to a pretty 
good-sized array on fibre-channel; it's fully HA, so there are four 
paths to any given LUN. My boot device, a 3Ware 9500-series SATA RAID 
card, ends up with a device name for it's first logical disk anywhere 
between /dev/sda and /dev/sdah; it's been /dev/sdu, /dev/sds, /dev/sdt, 
/dev/sdz, /dev/sdab, and pretty much everything in between, and it will 
vary from one boot to the next; it's at /dev/sdad right now.  But I have 
the 3ware card, an on-motherboard U320 SCSI controller, a four-port 
Silicon Image SATA card, and a dual-port FC card hooked to the SAN.