Page 28 mvEnterprise Release 4.1 on AIX Installation Guide
1.11 mvEnterprise Disk Flushing Program
This program is available on the AIX systems, and would normally
replace the native system
syncd
or
fsflush
daemons (background
processes). The program is mvEnterprise machine specific and performs
as follows:
·
The mvEnterprise database is divided into two segments; the space
above the system file base (
SYSBASE
) and the space below it,
enabling aggressive flushing of the data frames (those located above
SYSBASE). Flushing of the workspace frames (below SYSBASE) is
unnecessary.
·
The data space is divided into approximately equal sections (slices).
Each section on a single drive is
mmap
ed and flushed to disk. The
disk flusher then sleeps a prescribed amount of time and then
continues to the next section on the next disk drive.
·
This process allows flushing of the entire file system data space in
approximately in
n
x
m
(where
n
equals the number of sections and
m
equals the sleep time in seconds)
.
The defaults for the program
are 60 sections and a one-second sleep, so the data space is
synchronized to disk approximately once per minute.
NOTE
: The workspace below SYSBASE is not normally synchronized
(
sync
ed) since it contains no useful data in the event of a system
crash.
·
After completing a number of data space flush cycles (loops), the
program attempts to sync first the entire mvEnterprise virtual
machine and finally the entire system. The last step is necessary
because the user may have terminated the standard AIX
sync
ed
process.
·
The act of
sync
ing the entire machine may create the same
performance problems the user is attempting to avoid. To minimize
this possibility, most of the system should already be flushed before
issuing the
sync
request. The program performs the following tasks:
·
·
·
·
Changes the sleep setting on the last pass through the data
frames to a much smaller value.
Sync
s sections of the work space using this smaller sleep
time.
Executes
fsync
(an AIX system call) on the mvEnterprise
file systems with the smaller sleep time.
Issues the system wide
sync
.
