</section>
<section remap="h5">
<title>Description</title>
- <para>The <literal>filefrag</literal> utility reports the extent of fragmentation in a given file. Initially, <literal>filefrag</literal> attempts to obtain extent information using <literal>FIEMAP ioctl</literal>, which is efficient and fast. If <literal>FIEMAP</literal> is not supported, then <literal>filefrag</literal> uses <literal>FIBMAP</literal>.</para>
+ <para>The <literal>filefrag</literal> utility reports the extent of fragmentation in a given file.
+ The <literal>filefrag</literal> utility obtains the extent information
+ from Lustre files using the <literal>FIEMAP ioctl</literal>, which is
+ efficient and fast, even for very large files.</para>
+ <para>In default mode <footnote>
+ <para>The default mode is faster than the verbose/extent mode since
+ it only counts the number of extents.</para>
+ </footnote>, <literal>filefrag</literal> prints the number of physically
+ discontiguous extents in the file. In extent or verbose mode, each
+ extent is printed with details such as the blocks allocated on each OST.
+ For a Lustre file system, the extents are printed in device offset order
+ (i.e. all of the extents for one OST first, then the next OST, etc.),
+ not file logical offset order. If the file logical offset order was
+ used, the Lustre striping would make the output very verbose and
+ difficult to see if there was file fragmentation or not.</para>
<note>
- <para>The Lustre software only supports <literal>FIEMAP ioctl</literal>. <literal>FIBMAP
- ioctl</literal> is not supported.</para>
+ <para>Note that as long as a file has extent lengths of tens of
+ megabytes or more (i.e. <replaceable>read_bandwidth * seek_time >
+ extent_length</replaceable>), the read performance for the file will
+ not be significantly impacted by fragmentation, since file readahead
+ can fully utilize the disk disk bandwidth even with occasional seeks.
+ </para>
</note>
- <para>In default mode <footnote>
- <para>The default mode is faster than the verbose/extent mode.</para>
- </footnote>, <literal>filefrag</literal> returns the number of physically discontiguous
- extents in the file. In extent or verbose mode, each extent is printed with details. For a
- Lustre file system, the extents are printed in device offset order, not logical offset
- order.</para>
</section>
<section remap="h5">
<title>Options</title>
<para> <literal>-e</literal></para>
</entry>
<entry>
- <para>Uses the extent mode when printing the output.</para>
+ <para>Uses the extent mode when printing the output. This is
+ the default for Lustre files in verbose mode.</para>
</entry>
</row>
<row>
<para> <literal>-l</literal></para>
</entry>
<entry>
- <para>Displays extents in LUN offset order.</para>
+ <para>Displays extents in LUN offset order. This is the only
+ available mode for Lustre.</para>
</entry>
</row>
<row>
<para> <literal>-s</literal></para>
</entry>
<entry>
- <para>Synchronizes the file before requesting the mapping.</para>
+ <para>Synchronizes any unwritten file data to disk before
+ requesting the mapping.</para>
</entry>
</row>
<row>
<para> <literal>-v</literal></para>
</entry>
<entry>
- <para>Uses the verbose mode when checking file fragmentation.</para>
+ <para>Prints the file's layout in verbose mode when checking
+ file fragmentation, including the logical to physical mapping
+ for each extent in the file and the OST index.</para>
</entry>
</row>
</tbody>
<title>Examples</title>
<para>Lists default output.</para>
<screen>$ filefrag /mnt/lustre/foo
-/mnt/lustre/foo: 6 extents found</screen>
+/mnt/lustre/foo: 13 extents found</screen>
<para>Lists verbose output in extent format.</para>
- <screen>$ filefrag -ve /mnt/lustre/foo
-Checking /mnt/lustre/foo
+ <screen>$ filefrag -v /mnt/lustre/foo
Filesystem type is: bd00bd0
-Filesystem cylinder groups is approximately 5
-File size of /mnt/lustre/foo is 157286400 (153600 blocks)
-ext: device_logical: start..end physical: start..end: length: device: flags:
-0: 0.. 49151: 212992.. 262144: 49152: 0: remote
-1: 49152.. 73727: 270336.. 294912: 24576: 0: remote
-2: 73728.. 76799: 24576.. 27648: 3072: 0: remote
-3: 0.. 57343: 196608.. 253952: 57344: 1: remote
-4: 57344.. 65535: 139264.. 147456: 8192: 1: remote
-5: 65536.. 76799: 163840.. 175104: 11264: 1: remote
-/mnt/lustre/foo: 6 extents found</screen>
+File size of /mnt/lustre/foo is 1468297786 (1433888 blocks of 1024 bytes)
+ ext: device_logical: physical_offset: length: dev: flags:
+ 0: 0.. 122879: 2804679680..2804802559: 122880: 0002: network
+ 1: 122880.. 245759: 2804817920..2804940799: 122880: 0002: network
+ 2: 245760.. 278527: 2804948992..2804981759: 32768: 0002: network
+ 3: 278528.. 360447: 2804982784..2805064703: 81920: 0002: network
+ 4: 360448.. 483327: 2805080064..2805202943: 122880: 0002: network
+ 5: 483328.. 606207: 2805211136..2805334015: 122880: 0002: network
+ 6: 606208.. 729087: 2805342208..2805465087: 122880: 0002: network
+ 7: 729088.. 851967: 2805473280..2805596159: 122880: 0002: network
+ 8: 851968.. 974847: 2805604352..2805727231: 122880: 0002: network
+ 9: 974848.. 1097727: 2805735424..2805858303: 122880: 0002: network
+ 10: 1097728.. 1220607: 2805866496..2805989375: 122880: 0002: network
+ 11: 1220608.. 1343487: 2805997568..2806120447: 122880: 0002: network
+ 12: 1343488.. 1433599: 2806128640..2806218751: 90112: 0002: network
+/mnt/lustre/foo: 13 extents found</screen>
</section>
</section>
<section xml:id="dbdoclet.50438206_86244">
<para>When a client performs any remote operation, it gives the server a reasonable amount of time to respond. If a server does not reply either due to a down network, hung server, or any other reason, a timeout occurs which requires a recovery.</para>
<para>If a timeout occurs, a message (similar to this one), appears on the console of the client, and in <literal>/var/log/messages</literal>:</para>
<screen>LustreError: 26597:(client.c:810:ptlrpc_expire_one_request()) @@@ timeout
-
+
req@a2d45200 x5886/t0 o38->mds_svc_UUID@NID_mds_UUID:12 lens 168/64 ref 1 fl
-
+
RPC:/0/0 rc 0</screen>
</section>
</chapter>
git://git.whamcloud.com / doc / manual.git / commitdiff