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presto(8)
NAME
presto - Controls and monitors the Prestoserve file system accelerator
SYNOPSIS
/usr/sbin/presto [options]
OPTIONS
-d [filesystem ...]
Disables Prestoserve and writes the Prestoserve cache data to the
intended disks. If no file systems are specified, all accelerated file
systems are disabled, and the Prestoserve state is set to DOWN.
The filesystem parameter can be used to disable specific file systems.
You specify filesystem as a directory mount point (for example, /usr).
If no file systems are specified, all accelerated file systems are
disabled, and the Prestoserve state is set to DOWN.
Do not specify a block device because some functional subsystems, such
as the Advanced File System (AdvFS), can map more than one block device
to a mount point.
This option does not reset Prestoserve statistics.
The -d option takes effect before the -u or -R options.
-D [filesystem ...]
Similar to the -d option, but sets the Prestoserve state to DOWN only
if the specified directory is the root of a mounted file system.
Otherwise, the following message is displayed:
presto: directory is not a file system root
-F Flushes (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 as much of the
cache data as possible is written to the intended disks.
Note that unlike the -R option, the data in the Prestoserve cache
remains after it is written to the intended disks.
-l Lists the accelerated file systems and their mount points in a format
similar to the mount command. This option can be used with either NFS
client or server machines.
-L Lists all mounted file systems and their mount points 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 Displays Prestoserve information. The information includes the current
Prestoserve state; the statistics for write, read, and total
operations; and battery status. For example:
# /usr/sbin/presto -p
dirty = 52, clean = 7, inval = 903, 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, as follows:
· 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 on a write represents a physical disk
write that was avoided entirely, while a hit on a read represents
a physical disk read that was avoided.
· 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
presto -p 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.
The presto -p command also displays information about the Prestoserve
battery state. The command displays the battery state as ok, low, or
disabled.
Some processors support chargeable batteries and use self tests to
determine if a battery needs charging. If you use the presto -p command
on a machine that supports chargeable batteries, the battery state can
also be in self test or is charging. Note that if you use the dxpresto
command, batteries that are being self-tested or charged will be
displayed as disabled.
-R Writes as much of the Prestoserve cache data as possible to disk,
discards the data it could not write, purges all the Prestoserve
buffers, and sets the Prestoserve state to DOWN.
Unlike the -d option, the -R option discards the Prestoserve cache data
that could not be written to disk and resets the statistics
information. The option is useful when Prestoserve cache data is not
needed or if you cannot get Prestoserve out of the ERROR state.
Caution
Take care when using the -R option, because it destroys Prestoserve
cache data.
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 or
smaller than the default minimum size. If you specify a size that is
larger than the default maximum size, the default maximum size is used.
If you specify a size that is smaller than the default minimum size,
the default minimum size is used.
-u [filesystem ...]
Sets Prestoserve state to UP, and enables acceleration.
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.
The filesystem parameter can be used to enable specific file systems.
You specify filesystem as a directory mount point (for example, /usr).
Do not specify a block device because some functional subsystems, such
as the Advanced File System (AdvFS), can map more than one block device
to a mount point.
If Prestoserve state was ERROR, Prestoserve attempts to write any
blocks that are in the cache to disk to ensure that the previous error
condition has been corrected.
-U [filesystem ...]
Similar to the -u option, but sets the Prestoserve state to UP only if
the specified directory is the root of a mounted file system.
Otherwise, the following message is displayed:
presto: directory is not a file system root
-v Specifies verbose mode. This option prints extra information to
standard output. The information can be used for debugging purposes.
DESCRIPTION
The presto command allows you to accelerate file systems, obtain
Prestoserve status, and administer Prestoserve.
If invoked with no options, presto 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 batteries.
When the Prestoserve state is UP, Prestoserve improves I/O performance to
accelerated file systems by caching synchronous disk write operations to
nonvolatile memory.
When the Prestoserve state is DOWN, all I/O requests are passed to the
appropriate disks.
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.
FILES
/dev/pr0
Generic Prestoserve control device.
SEE ALSO
Commands: prestoctl_svc(8), prestosetup(8), dxpresto(8X)
Files: prestotab(4)
Networking: presto(7)
Guide to Prestoserve
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Index for
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Alphabetical
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Top of
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