Vijay Adik vadik@us - IBM
Vijay Adik vadik@us - IBM
Vijay Adik vadik@us - IBM
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<strong>IBM</strong> Advanced Technical Support - Americas<br />
Other I/O Stack Tuning Options (Device Level)<br />
lsattr/chdev:<br />
� num_cmd_elems = maximum number of outstanding I/Os for an adapter.<br />
� queue_depth = the maximum # of outstanding I/Os for an hdisk.<br />
Recommended/supported maximum is storage subsystem dependent.<br />
� max_xfer_size = the maximum allowable I/O transfer size (default is 0x100000 or 256k).<br />
Maximum supported value is storage subsystem dependent. Increasing value (to at<br />
least 0x200000) will also increase DMA size from 16 MB to 256 MB.<br />
� dyntrk = When set to yes (recommended), allows for immediate re-routing of I/O<br />
requests to an alternative path when a device ID (N_PORT_ID) change has been<br />
detected.<br />
� fc_err_recov = When set to “fast_fail” (recommended), if the driver receives an RSCN<br />
notification from the switch, the driver will check to see if the device is still on the<br />
fabric and will flush back outstanding I/Os if the device is no longer found.<br />
© 2009 <strong>IBM</strong> Corporation<br />
April 17, 2009
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