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presto(8) System Manager's Manual presto(8) NAME presto - Controls and monitors the Prestoserve file system accelerator SYNOPSIS /usr/sbin/presto [flags] DESCRIPTION The presto command allows you to accelerate file systems, obtain Prestoserve status, and administer Prestoserve. If invoked with no flags, 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 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 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 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. FLAGS Disables Prestoserve and writes the Prestoserve cache data to the in- tended disks. Only those file systems specified by filesystem are dis- abled. You specify filesystem as a directory mount point (for example, /usr). Do not specify a block device because some functional subsys- tems, such as the Advanced File System (AdvFS), can map more than one block device to a mount point. If no file systems are specified, all accelerated file systems are disabled, and the Prestoserve state is set to DOWN. This flag does not reset Prestoserve statistics. The -d flag takes effect before the -u or -R flags. Similar to the -d flag, but sets the Prestoserve state to DOWN only if the specified directory is the root of a mounted file system. Oth- erwise, the following message is displayed: presto: directory is not a file system root Writes the Prestoserve cache data to the intended disks, but leaves the cache data intact. If the flag is used and the Prestoserve state is UP, then the cache data is written to the intended disks, and the state re- mains 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 flag, the data in the Prestoserve cache remains after it is written to the intended disks. Invokes the specified operations on the remote machine hostname by using an RPC protocol. The remote machine must be running the prestoctl_svc daemon to allow the use of the -h flag. The prestoctl_svc -n flag is required to allow the use of -h with the -s, -d, and -u administrative flags. See prestoctl_svc(8) for details. To avoid possible security and performance prob- lems, Digital strongly recommends against using the -h option. See the rsh(1) reference page for alternative methods to use for remote operations. Lists the accelerated file systems and their mount points in a format similar to the mount command. This flag can be used with either NFS client or server machines. Lists all local and remote 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: Instead of directly accessing the non- volatile memory, the file system's device receives the Prestoserve data only after the data is first copied to main memory. Prestoserve acceleration is not enabled on the file system. An error occurred using the file system, and the Prestoserve cache data has still not been written successfully to the intended disks. Displays Prestoserve information. The information includes the current Prestoserve state; the statis- tics for write, read, and total operations; and battery status. For example: # /usr/sbin/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, 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 dirty hit on a read represents the same condition for a disk read. 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 de- vice 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 com- puted 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 and is running Prestoserve locally, the battery state can also be in self test or is charging. Note that if you use the -p flag with the -h flag (or if you use the dxpresto command, batteries that are being self-tested or charged will be displayed as disabled. 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 flag, the -R flag discards the Prestoserve cache data that could not be written to disk and resets the statistics information. The flag is useful when Prestoserve cache data is not needed or if you cannot get Prestoserve out of the ERROR state. Take care when using the -R flag, because it destroys Prestoserve cache data. The -R flag takes effect before the -u flag. 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 flag 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 flag 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 de- fault maximum size. If you specify a size that is larger than the default maximum size, the default maximum size is used. Sets Prestoserve state to UP, and enables acceleration. Only those file systems specified by filesystem are enabled. You specify filesystem as a directory mount point (for example, /usr). Do not specify a block device because some functional subsys- tems, such as the Advanced File System (AdvFS), can map more than one block device to a mount point. If no file systems are specified, all local writable file sys- tems that are mounted will have Prestoserve enabled. File sys- tems that are presently accelerated will remain accelerated. If Prestoserve state was ERROR, Prestoserve attempts to write any blocks that are in the cache to disk to ensure that the pre- vious error condition has been corrected. Similar to the -u flag, 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 Specifies verbose mode. This flag prints extra information to standard output. The information can be used for debugging purposes. FILES RELATED INFORMATION prestoctl_svc(8), dxpresto(8X), presto(7), prestotab(4), prestosetup(8) Guide to Prestoserve delim off presto(8)