26 hard drive limit on x86 servers, IBM x3650, Dell PE 2950, Dell PE 2850, where is my limitation?

Solution 1:

There is no such limit. However, the naming convention in linux is slightly different after the first 26 device names (/dev/sdaa is the next after /dev/sdz). The hard limit on linux is, if memory serves, 128 SCSI disks (which includes SAS and SATA disks typically), after which you will run out of allocated device numbers. Anyway, I strongly suspect your vendor's support is in error (at least they should have identified the 128-device limit).

Very few distributions include a /dev which contains device names after /dev/sdz, so if the contents of /dev are not being constructed at runtime (as they commonly are) and a static /dev is set up, it's possible that this might be the cause; if you can get a shell, add a device using mknod /dev/sdaa 65 160 to create a reference to the 27th disk. You may then be able to operate on it.

The device number is calculated in this way. The major will be either 8 (first 64 drives) or 65 (last 64 drives). The minor number increases in increments of 16 per drive, resulting in 16 minor numbers for the same volume; the 0th represents the whole device, and the 1st to 15th represent partitions (only 15 partitions per device are permitted).

You may also want to try a recent livecd of something (ubuntu or gentoo or anything, as long as it is reasonably recent) to see if the devices are detected there. Also check dmesg to ensure your kernel is actually finding them.