Managing NFS and KRPC Kernel Configurations in HP-UX 11i v3 (762807-001, March 2014)

on HP-UX 11i v3). When an NFS client mounts a filesystem with the forcedirectio option, data is
transferred directly between the client and server without buffering on the client.
By default the direct I/O data transfers are synchronous, where the client sends a single write request
to the server and waits for the server to respond with the requested data before initiating a new
request. Enabling the nfs3_enable_async_directio_write tunable allows the client to send several I/O
requests in parallel before waiting for the server's response. The number of parallel direct I/O
requests is configurable via the nfs3_max_async_directio_requests tunable. This can greatly improve
write performance for applications that use direct I/O. Currently this feature is supported only for TCP
traffic.
Tested Values
Default: 0 (Tunable is disabled)
Min: 0
Max: 1 (Tunable is enabled)
Restrictions on Changing
• The nfs3_enable_async_directio_write tunable is dynamic. System reboot is not required to
activate a change made to this tunable.
• Only NFSv3 TCP mount points that are mounted with forcedirectio options are affected by
changing the value of this tunable.
Modifying the Value
If an application experiences poor write performance on an NFS filesystem mounted with the
forcedirectio option, enabling the nfs3_enable_async_directio_write tunable can improve the write
performance.
2.1.24 nfs3_jukebox_delay
Description
The nfs3_jukebox_delay tunable specifies the time interval the NFS client must wait after receiving the
NFS3ERR_JUKEBOX error before retransmitting the request to the server.
If an NFS client requests a file on the server, and if the file is unavailable because it resides on a slow
media or has been migrated on an HSM storage device, the server generates the NFS3ERR_JUKEBOX
error. If the server returns this error, it indicates that the file cannot be accessed for a considerable
amount of time. The retransmission of the request depends on the time interval specified by this
tunable.
Tested Values
Default: 1000 (10 seconds)
Min: 100 (1 second)
Max: 60000 (600 seconds)
Note: If the tunable is set to a value less than 100 or greater
than 60000, an informational warning is issued at runtime.
These values are outside the tested limits.