4
Disk Formatting
Chapter 4 provides instructions for formatting the DECmpp 12000/Sx parallel
disk array (PDA) disks. The PDA has been configured, inspected, and tested in
the factory. The information presented in this chapter is not required to install a
PDA. It is intended for Digital Services personnel.
Because both the disk system area and the user area must be formatted, disk
formatting is a two-step process. Read the associated
man page
(s) first.
The following example shows a typical format sequence for a new bank:
# daformat -b1 -f2 -A /dev/da0a
# daformat -b1 -f3 -A /dev/da0a
Always use function 2 (
-f2
) when formatting the system area. Function 2
reads the manufacturer’s media defect information and saves it in the system
area. During the user area formatting, bad blocks are mapped using this defect
information.
In the following descriptions, all numbers are in decimal form except when
followed by the letter
h
(for example, 10h), which indicates a hexadecimal value.
The first time a controller is brought up, run the
dainit(8)
command to initialize
it.
4.1 The FORMAT Command
Formatting is the process of writing sector headers on each track of a disk. The
FORMAT (
daformat(8)
) command formats selected disks within a bank.
When formatting disks, the disk array (DA) controller reserves at least one sector
per track as a spare. If a single media flaw is logged on a track, the spare sector
is placed on the single media flaw. (Every track can tolerate one bad sector.)
If two or more sectors within one track have logged media flaws, the track is
considered bad and is assigned an alternate track during format.
Formatting a disk consists of two distinct operations:
• Initializing the system area
• Formatting the user area (system area already exists)
Formatting operations occur independently of the drive mount status or the bank
online status; the target drive needs only to be on line (power on and ready or
spun up).
A bank’s Flaw Descriptor Table (FDT) is generated from the Raw Flaw Table
(RFT) and is used to assign alternate tracks. The FDT is generated only during a
Bank Mount Sequence. Certain formatting operations (
func 0
,
func 1
, and
func
2
) do not alter a bank’s FDT in any way.
After formatting, run the MOUNTBANK command (
damount(8)
), as appropriate.
Disk Formatting 4–1
