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Lustre 1.6 Operations Manual

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20.2.5 Watching the OST Block I/O Stream<br />

Similarly, there is a brw_stats histogram in the obdfilter directory which shows<br />

you the statistics for number of I/O requests sent to the disk, their size and whether<br />

they are contiguous on the disk or not.<br />

cat /proc/fs/lustre/obdfilter/lustre-OST0000/brw_stats<br />

snapshot_time:<br />

1174875636.764630 (secs:usecs)<br />

read<br />

write<br />

pages per brw brws % cum % | rpcs % cum %<br />

1: 0 0 0 | 0 0 0<br />

read<br />

write<br />

discont pages rpcs % cum % | rpcs % cum %<br />

1: 0 0 0 | 0 0 0<br />

read<br />

write<br />

discont blocks rpcs % cum % | rpcs % cum %<br />

1: 0 0 0 | 0 0 0<br />

read<br />

write<br />

dio frags rpcs % cum % | rpcs % cum %<br />

1: 0 0 0 | 0 0 0<br />

read<br />

write<br />

disk ios in flight rpcs % cum % | rpcs % cum %<br />

1: 0 0 0 | 0 0 0<br />

read<br />

write<br />

io time (1/1000s) rpcs % cum % | rpcs % cum %<br />

1: 0 0 0 | 0 0 0<br />

read<br />

write<br />

disk io size rpcs % cum % | rpcs % cum %<br />

1: 0 0 0 | 0 0 0<br />

read<br />

write<br />

The fields are explained below:<br />

Field<br />

pages per brw<br />

discont pages<br />

discont blocks<br />

Description<br />

Number of pages per RPC request, which should match aggregate client<br />

rpc_stats.<br />

Number of discontinuities in the logical file offset of each page in a<br />

single RPC.<br />

Number of discontinuities in the physical block allocation in the<br />

filesystem for a single RPC.<br />

20-18 <strong>Lustre</strong> <strong>1.6</strong> <strong>Operations</strong> <strong>Manual</strong> • September 2008

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