presto(8)presto(8)Namepresto - 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 soft‐
ware 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 condi‐
tions 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 accel‐
erated 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
command 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 acceler‐
ated. Any unusual Prestoserve state for a file system is dis‐
played 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 suc‐
cessfully 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:
· The clean hits counter shows the number of hits (block
matches) on the clean buffers.
· 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.
· The allocations counter shows the number of new buffers that
had to be allocated for disk block images.
· 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
counters 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 information 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 exam‐
ple, 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 accelerated 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 Alsorc(8), prestoctl_svc(8), dxpresto(8X), presto(4)
Guide to Prestoserve
presto(8)
