tunedasd - A tool to adjust tunable parameters on DASD devices
[OPTION] COMMAND device
is a tool to adjust tunable parameters on DASD devices. It can
be used to modify the status of the device and to adjust some performance
relevant settings. The DEVICE is the node of the device (e.g. '/dev/dasda') or
a list of devices separated by a space character. Following functions are
- Get and reset the performance statistics profile per
- Get and set the caching mode of the storage server. This is
only available for ECKD devices, because it is implemented using ECKD
Channel Program commands.
- Reserve/Release/Unconditional Reserve a device. This is
only available for ECKD devices, because it is based on the Control Unit
is called without parameter, it prints a short usage
information and exits.
- -v or --version
- Print version information, then exit.
- -h or --help
- Print usage information, then exit.
- -g or --get_cache
- Get current storage server caching behavior.
- -c or --cache <behavior>
- Define caching behavior on storage server. The following
caching behaviors are currently supported by modern Enterprise Storage
- normal ('Normal Cache replacement'),
- bypass (Bypass Cache),
- inhibit (Inhibit Cache Loading),
- sequential (Sequential Access),
- prestage (Sequential Prestage),
- record (Record Access)
- More details about caching can be found in the 'Storage
Control Reference' of the attached storage server.
- -n or --no_cyl <n>
- Number of cylinders to be cached (only valid together with
- -S or --reserve
- Reserve device.
- -L or --release
- Release device.
- -O or --slock
- Unconditional reserve device.
Note: Use with care, this breaks an existing reserve.
- -P or --profile
- Print profile info of device.
Note: Profile info must be available and enabled ('echo set on >
/proc/dasd/statistics') in the kernel to get valid results out of the
- -Q or --query_reserve
- Query the current reserve status of the device. The
following states are defined:
- none: The device is not reserved.
- implicit: The device is not reserved, but there is a
contingent or implicit allegiance to this Linux instance.
- other: The device is reserved to another operating
- reserved: The device is reserved to this Linux
- More details about reserve/release can be found in the
'Storage Control Reference' of the attached storage server.
- -I or --prof_item <row>
- Print single profile item data row (without header).
Following rows are supported:
- reqs (# of dasd I/O requests),
- sects (# of 512Byte sectors),
- sizes (Histogram of sizes),
- total (Histogram of I/O times),
- totsect (Histogram of I/O times per sector),
- start (Histogram of I/O time till ssch),
- irq (istogram of I/O time between ssch and
- irqsect (istogram of I/O time between ssch and irq
- end (Histogram of I/O time between irq and
- queue (# of req in chanq at enqueuing)
- -R or --reset_prof
- Reset profile info of device.
- -p or --path_reset <chpid>
- Reset a channel path <chpid> of a selected device. A
channel path might be suspended due to high IFCC error rates or a High
Performance FICON failure. Use this option to resume considering the
channel path for I/O.
- Reset all channel paths of the selected device. The channel
paths might be suspended due to high IFCC error rates or a High
Performance FICON failure. Use this option to resume considering all
defined channel paths for I/O.
1. Scenario: Get profile info for a device.
tunedasd -P /dev/dasdc
tunedasd -PI irq /dev/dasdc
2. Scenario: Set device caching mode to 1 cylinder 'prestage'.
tunedasd -c prestage -n 1 /dev/dasdc
3. Scenario: Reset failed channel path with CHPID 45
tunedasd -p 45 /dev/dasdc