presto.8

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH presto 8 
.SH Name
presto \- control and monitor the Prestoserve file system accelerator 
.SH Syntax
.B /usr/etc/presto
[
\fIoptions\fR
]
.SH Description
.NXR "presto command"
The 
.PN presto
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.
.PP
If invoked with no options, 
.PN 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.
.PP
When the Prestoserve state is UP, Prestoserve
improves I/O performance to accelerated file systems 
by caching synchronous disk write operations to nonvolatile memory.
.PP
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
.PN presto
command should be added to your 
.PN /etc/rc.local
file to enable file system acceleration when the machine reboots.
.PP
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.  
.PP
Also, if there is insufficient backup battery power, 
Prestoserve will enter the ERROR state.
.PP
By default, all local writable file systems that are mounted 
are accelerated when Prestoserve is brought up.
.SH Options
.IP "\-d [\fIfilesystem...\fR] [\fIblkdev...\fR]" 
Disables Prestoserve and writes the Prestoserve cache data to the intended 
disks.  Only those file systems specified by 
\fIfilesystem\fR are disabled.  You can specify \fIfilesystem\fR as a
mounted block device (for example, 
.PN /dev/ra3g )
or as a directory mount point (for example, 
.PN /usr) .
You can specify \fIblkdev\fR for an unmounted block device
(for example, 
.PN /dev/ra0c) .  
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.  
.IP
This option does not reset Prestoserve statistics. 
.IP
The \fB\-d\fR option takes effect before the \fB\-u\fR or \fB\-R\fR
options.
.IP "\-F"
Writes the Prestoserve cache data to the intended disks,
but leaves the cache data intact.  
.IP
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.  
.IP
Note that unlike the \fB\-R\fR
option, the data in the Prestoserve cache remains after it is written to
the intended disks.
.IP "\-h \fIhostname\fR" 
Invokes the specified operations on the remote machine \fIhostname\fR by 
using an RPC protocol.  You can use the \fB\-h\fR option with other 
.PN presto
command options, but the protocol does not support the
\fB\-R\fR or \fB\-L\fR
options.  The remote machine must be running the 
.PN prestoctl_svc
daemon to allow the use of the \fB\-h\fR option.  However, 
the remote machine must be running
.PN prestoctl_svc
.PN \-n
option to allow the use of the 
\fB\-h\fR option and the \fB\-u,\fR \fB\-d,\fR 
and \fB\-s\fR administrative options.  See
.MS prestoctl_svc 8
for more details.
.IP \-l 
Lists the accelerated file systems and their mount points in a format
similar to the 
.PN mount 
command.  This option can be used with either NFS client or server machines.
.IP \-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:
.RS 
.IP bounceio 10
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.
.IP disabled 10
Prestoserve acceleration is not enabled on the file system.
.IP error 10
An error occurred using the file system,
and the Prestoserve cache data has still not been written successfully
to the intended disks.
.RE
.IP \-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:
.EX
# \f(CB/usr/etc/presto -p\fP
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
.EE
.IP
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.
.IP
For each Prestoserve cache read or write operation, Prestoserve increments
a counter:
.RS
.IP \(bu 4
The clean hits counter shows the number of hits (block matches) on the clean
buffers.
.IP \(bu 4
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.
.IP \(bu 4
The allocations counter shows the number of new buffers that had to be allocated 
for disk block images. 
.IP \(bu 4
The passes counter shows the number of I/O operations that Prestoserve
passed directly to the real device driver.
.RE
.IP
In addition, for each Prestoserve cache read or write operation, the 
.PN "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.
.IP \-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.  
.IP
Unlike the \fB\-d\fR option, the \fB\-R\fR
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 \fB\-R\fR
option destroys Prestoserve cache data, it should be used carefully. 
.IP
The \fB\-R\fR option takes effect before the \fB\-u\fR option.  
.IP "\-s \fIsize\fR" 
Sets the size of the Prestoserve cache to \fIsize\fR
bytes.  The \fIsize\fR can be specified using the
decimal or hexadecimal conventions.  For example, both 262144 and 0x40000
represent 256 Kbytes. 
.IP
If the \fB\-s\fR
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.
.IP
You may want to use the \fB\-s\fR 
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 \fIsize\fR 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.
.IP "\-u [\fIfilesystem...\fR] [\fIblkdev...\fR]" 
Sets Prestoserve state to UP, and enables acceleration.
.IP
Only those file systems specified by \fIfilesystem\fR are
enabled.  You can specify \fIfilesystem\fR as a
mounted block device (for example, 
.PN /dev/ra3g )
or as a directory mount point (for example, 
.PN /usr) .  
You can specify \fIblkdev\fR for an unmounted block device
(for example, 
.PN /dev/ra0c) .
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.
.IP
If the Prestoserve state was DOWN, this option 
resets the Prestoserve statistics and buffers to their 
initial values.  
.IP
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.
.IP \-v 
Specifies verbose mode.  This option prints extra information to standard 
output.  The information can be used for debugging purposes.
.SH Files
.TP 18
.PN /dev/pr0
Generic Prestoserve control device.
.TP 18
.PN /etc/rc.local
File where you add the 
.PN "presto -u"
command to accelerate file systems after a reboot.
.SH See Also
rc(8), prestoctl_svc(8), dxpresto(8X), presto(4)
.br
\fIGuide to Prestoserve\fP