Logical Volume Manager Basics

High Level Commands• Commands used by SMIT
• Commands used by users in command line or shell
scripts
• High levels of error checking

Intermediate Commands
Notes: The Intermediate commands are all C binaries:
getlvcb, getlvname, getlvodm, getvgname, lvgenmajor, lvgenminor, lvrelmajor, lvrelminor, putlvcb, putlvodm, lchangelv,
lcreatelv, ldeletelv, lextendlv, lquerylv, lreducelv, lresynclv, lchangepv, ldeletepv, linstallpv, lquerypv, lresyncpv, lcreatevg,
lqueryvg, lqueryvgs, lvaryonvg, lvaryoffvg, lresynclp, lmigratepp.
The commands are called by the High Level command shell scripts.

Library Calls - API
• Library calls to be used as Application Program Interface
It lets programmers access the LVM layer directly through the library layer provided by /usr/lib/liblvm.a.

LVM Device Driver• Access same as those for typical IBM device driver
• Checking provided, but assumes user has basic device
driver knowledge
• Rarely used. If used wrong, disastrous results!

Notes: The LVM device driver comes in two portions, the pinned portion and the non-pinned portion. The pinned portion is called /usr/lib/drivers/hd_pin and /usr/lib/drivers/hd_pin_bot. Before AIX 4.1, the driver was just called hd_pin and the entire driver was pinned into memory (not pageable). With AIX 4.1, the driver’s true non-pageable portion is in hd_pin_bot and the hd_pin is now pageable. The LVM device driver is either called by the jfs filesystem or the lvm library routines.
When a request is received by the LVM device driver, it calls the disk device driver.

Disk Device Driver• Access same as those for typical IBM device driver
• Sometimes other vendors use the disk device driver as pseudo driver for their products

Note:The most common disk device driver is the one for scsi device drivers,
/usr/lib/drivers/scdisk and /usr/lib/drivers/scdiskpin. The second most common disk device driver is probably the one for the 9333 serial dasd device. This is found in the binaries /usr/lib/drivers/sd and /usr/lib/drivers/sdpin. In both device drivers, the portion called “pin” is that which is pinned into memory and cannot be paged out of memory. When a request from the LVM device driver is received by the disk device driver, the request is packaged and then transferred down to the scsi device drivers.