4.3 The RECONSTRUCT Command
Once a standby drive is in operation (replacing an inoperable data/parity drive),
the bank can tolerate another drive failure. If the next drive to fail is another
data/parity drive, mark it disabled, using the
dadsbl(8)
command to set the
DSBL field to the failed drive’s number. Entering the
darecon(8)
command at
this point results in either the DSBL drive or the SUBS drive being reconstructed,
depending on the value of target. This action falls under Case 4 in Table 4–1.
When you physically replace an inoperable data/parity drive with a new drive
and a standby drive is in operation replacing the original drive, bring the new
drive on line by entering the
damount(8)
command, followed by the
darecon(8)
command. On successful reconstruction, the SUBS field is automatically set to 0,
deassigning the standby drive. This action falls under Case 5 in Table 4–1.
Finally, if a standby drive becomes inoperable while it is assigned to replace a
data/parity drive:
• If no other drive is inoperable (DSBL = 0 and SUBS = X):
1. Set DSBL = Ah.
2. Enter a
damount(8)
command.
The DA controller immediately sets DSBL equals X and SUBS equals 0,
deassigning the standby and restoring the disabled status of the previously
substituted drive. This deassigns the standby drive and informs the DA
controller that the drive it was formerly replacing is still inoperable.
• If another drive is inoperable (DSBL nonzero), the bank is unusable.
4.4 The SCRUB Command
The SCRUB command (
dascrub(8)
) initiates a digital surface analysis of selected
disk drives (previously formatted) within a bank.
The
func
field defines the function’s performance as follows:
• 0h — Read check only. Preserves disk data.
• 1h — Write 00000000h, then read check. Overwrites disk data.
• 2h — Write FFFFFFFFh, then read check. Overwrites disk data.
• 3h — Write AAAAAAAAh, then read check. Overwrites disk data.
• 4h — Write 55555555h, then read check. Overwrites disk data.
• 5h — Write CCCCCCCCh, then read check. Overwrites disk data.
• 6h — Write 33333333h, then read check. Overwrites disk data.
• 7h — Write 6DB6DB6Dh, then read check. Overwrites disk data.
• 8h — Write 92492492h, then read check. Overwrites disk data.
• 9h — Write C6DEC6DEh, then read check. Overwrites disk data.
• Ah — Write 39213921h, then read check. Overwrites disk data.
• Bh, Ch, Dh, Eh — Reserved (0s). Overwrites disk data.
• Fh — Write random, then read check. Overwrites disk data.
Depending on the
func
field, the operation will read-only the entire disks or
write/read the entire disks, and then log any media errors encountered into the
GET.
4–8 Disk Formatting
