presto(8) System Manager's Manual presto(8)
Name
presto - control and monitor the Prestoserve file system accelerator
Syntax
/usr/etc/presto [ options ]
Description
The command allows you to get Prestoserve information and to administer Prestoserve from a local machine that is running the Prestoserve
software or from a remote machine that is running the Prestoserve software.
If invoked with no options, displays the Prestoserve state (either UP, DOWN, or ERROR), the number of bytes of nonvolatile memory the
Prestoserve cache is using, how long the cache has been enabled, the write cache efficiency, and the state of the backup battery or batter-
ies.
When the Prestoserve state is UP, Prestoserve improves I/O performance to accelerated file systems by caching synchronous disk write opera-
tions to nonvolatile memory.
When the Prestoserve state is DOWN, all I/O requests are passed to their intended devices. Because the Prestoserve state is DOWN after a
reboot, the command should be added to your file to enable file system acceleration when the machine reboots.
If it detects a disk error during a write back, Prestoserve enters the ERROR state and disables itself. However, Prestoserve continues to
maintain the integrity of cached data. Some possible disk error conditions are: the disk drive is write protected or off line, a cable
problem exists, or a bad disk block exists.
Also, if there is insufficient backup battery power, Prestoserve will enter the ERROR state.
By default, all local writable file systems that are mounted are accelerated when Prestoserve is brought up.
Options
-d [filesystem...] [blkdev...]
Disables Prestoserve and writes the Prestoserve cache data to the intended disks. Only those file systems specified by filesystem
are disabled. You can specify filesystem as a mounted block device (for example, or as a directory mount point (for example, You
can specify blkdev for an unmounted block device (for example, If no file systems or block devices are specified, all accelerated
file systems and unmounted block devices are disabled, and the Prestoserve state is set to DOWN.
This option does not reset Prestoserve statistics.
The -d option takes effect before the -u or -R options.
-F Writes the Prestoserve cache data to the intended disks, but leaves the cache data intact.
If the option is used and the Prestoserve state is UP, then the cache data is written to the intended disks, and the state remains
UP. If the Prestoserve state is DOWN, then there is no data to write to the disks, and the state remains DOWN. If the state is
ERROR, then the cache data is written to the intended disks if possible.
Note that unlike the -R option, the data in the Prestoserve cache remains after it is written to the intended disks.
-h hostname
Invokes the specified operations on the remote machine hostname by using an RPC protocol. You can use the -h option with other com-
mand options, but the protocol does not support the -R or -L options. The remote machine must be running the daemon to allow the
use of the -h option. However, the remote machine must be running option to allow the use of the -h option and the -u, -d, and -s
administrative options. See for more details.
-l Lists the accelerated file systems and their mount points in a format similar to the command. This option can be used with either
NFS client or server machines.
-L Lists all local and remote mounted file systems and their mount points, in addition to any block devices that have been accelerated.
Any unusual Prestoserve state for a file system is displayed after the mount point. The unusual states include:
bounceio Instead of directly accessing the nonvolatile memory, the file system's device receives the Prestoserve data only after
the data is first copied to main memory.
disabled Prestoserve acceleration is not enabled on the file system.
error An error occurred using the file system, and the Prestoserve cache data has still not been written successfully to the
intended disks.
-p Prints Prestoserve information. The information is grouped into two areas: the current Prestoserve state and the statistics for
write, read, and total operations. For example:
# /usr/etc/presto -p
dirty = 52, clean = 7, inval = 0, active = 2
count hit rate clean hits dirty hits allocations passes
write: 1516 65% 0 989 511 15
read: 8 0% 0 0 0 8
total: 1524 65% 0 989 511 23
state = UP, size = 0x7e000 bytes
statistics interval: 00:00:13 (13 seconds)
write cache efficiency: 66%
All batteries are ok
The current Prestoserve statistics account for all Prestoserve buffers. A dirty buffer contains a disk block image that has not
been written to disk. A clean buffer contains a valid disk block image that has been written to disk. An inval buffer does not
presently contain a disk block image. An active buffer is currently in transition to disk, meaning that a write operation has
started but has not completed on that buffer.
For each Prestoserve cache read or write operation, Prestoserve increments a counter:
o The clean hits counter shows the number of hits (block matches) on the clean buffers.
o The dirty hits counter shows the number of hits on the dirty buffers. Each dirty hit represents a physical disk write that was
avoided entirely.
o The allocations counter shows the number of new buffers that had to be allocated for disk block images.
o The passes counter shows the number of I/O operations that Prestoserve passed directly to the real device driver.
In addition, for each Prestoserve cache read or write operation, the command displays the count, which is the sum of the four coun-
ters explained previously; the hit rate percentage, which is the ratio of clean hits and dirty hits to the total count and which
indicates the effectiveness of the Prestoserve cache; and the write cache efficiency percentage, which is computed from the ratio of
write dirty hits to the number of writes copied into the Prestoserve cache.
-R Writes the Prestoserve cache data to the intended disks, sets the Prestoserve state to DOWN, purges all Prestoserve buffers, and
resets the Prestoserve write and read statistics.
Unlike the -d option, the -R option discards the Prestoserve cache data that could not be written to the intended disks. The option
is useful when Prestoserve cache data is not needed. You should note that, because the -R option destroys Prestoserve cache data,
it should be used carefully.
The -R option takes effect before the -u option.
-s size
Sets the size of the Prestoserve cache to size bytes. The size can be specified using the decimal or hexadecimal conventions. For
example, both 262144 and 0x40000 represent 256 Kbytes.
If the -s option is used and the current Prestoserve state is UP, the state is set to DOWN, the Prestoserve cache is resized, and
the state is set to UP.
You may want to use the -s option to determine how Prestoserve performs with a reduced amount of nonvolatile memory. Note that the
size of the Prestoserve cache cannot be larger than the default maximum size. If you specify a size that is larger than the default
maximum size, the default maximum size is used. Refer to the appropriate appendix for your processor in the %%DRPresto%% for infor-
mation about the default maximum size of nonvolatile memory.
-u [filesystem...] [blkdev...]
Sets Prestoserve state to UP, and enables acceleration.
Only those file systems specified by filesystem are enabled. You can specify filesystem as a mounted block device (for example, or
as a directory mount point (for example, You can specify blkdev for an unmounted block device (for example, If no file systems are
specified, all local writable file systems that are mounted will have Prestoserve enabled. File systems that are presently acceler-
ated will remain accelerated.
If the Prestoserve state was DOWN, this option resets the Prestoserve statistics and buffers to their initial values.
If Prestoserve state was ERROR, Prestoserve attempts to write any blocks that are in the cache to the intended disks to make sure
that the previous error condition has been corrected.
-v Specifies verbose mode. This option prints extra information to standard output. The information can be used for debugging pur-
poses.
Files
Generic Prestoserve control device.
File where you add the
command to accelerate file systems after a reboot.
See Also
rc(8), prestoctl_svc(8), dxpresto(8X), presto(4)
Guide to Prestoserve
presto(8)