IBM s/390 manual Ultrabay, Using a second Linux hard disk, # cat /proc/partitions

5.5 Ultrabay

ThinkPad A21 and A22 units have a “bay” that can hold a CD-ROM drive, or a diskette drive, or a second hard disk drive—but only one at a time. Current Windows operating systems permit the user to change these devices while the system is running. We were unable to make clean (without side effects) changes under Linux, while Linux was running. We found it was easier to shut down Linux, let the ThinkPad power down, and then swap devices in the Ultrabay. Linux detected the new device correctly when it was restarted.

5.5.1 Using a second Linux hard disk

The preparation and use of a second hard disk is discussed in “Ultrabay” on page 42. After it was available, we created three 3390-1 work volumes on the second hard disk. The following FLEX-ES commands, issued from a Linux Terminal window, will do this:

The ckdfmt commands take some time to run because both write the complete emulated 3390 volume. The -nflag in ckdfmt prevents a verification pass to read the formatted data just written. These commands do not perform S/390 operating system initialization. After OS/390 is running, we will need to use ICKDSF to initialize the volumes.

We obtained a second 32 GB hard disk drive (IBM part number 08K9511), along with the mounting tray (IBM part number 08K6068) needed to use it in the Ultrabay. We removed the CD-ROM drive and installed the second hard disk while the ThinkPad was turned off. We turned power on and let Linux boot. We then determined the Linux identity of the second drive:

#cat /proc/partitions

major	minor	#blocks	name	(.... more data .....)
3	0		hda
3	1	nnnnn	hda1
3	2	nnnnn	hda2
..	..	....	....
22	0	31253040	hdc	0 0 0 0 0 0 0 0 0 0 0

The first hard disk (internal in the ThinkPad) is /dev/hda; looking at the above listing, we see a second hard disk as /dev/hdc. This drive (as expected for a new disk) had no partitions. (We do not know why Linux selected hdc instead of hdb, which would logically be next in sequence.)

We decided to create two file systems on the second hard disk. One would be about 2 GB and use mount point /holding. The other would use all the remaining space and have mount point /s391. We intended to use /holding for compressed tar images (created as backups) and other temporary files and we might have considerable creation/deletion activity in this file system. The /s391 file system would be solely for emulated S/390 volumes. Using two file systems seemed to reduce the chances for significant fragmentation of emulated volume files.6

We also noted that IBM, like most other manufacturers, uses decimal numbers to describe disk capacity (1M = 1,000,000) while Linux utilities typically use power-of-two numbers (1M = 1,048,576). Using Linux numbers, the capacity of the disk was about 29 GB.

6We may have been too sensitive about fragmentation. Experienced Linux users claim there are practically no fragmentation effects in normal Linux file systems. However, they admit that FLEX-ES operation (57 KB reads or writes when emulating a 3390) is not typical Linux I/O. We felt that disk I/O may be the weakest point of ThinkPad/EFS performance and felt that avoiding fragmentation might help performance. The author welcomes any measurement data (on an EFS system) that may help resolve this issue.

42S/390 PID: ThinkPad Enabled for S/390