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- FSCMD User Commands FSCMD
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- _________________________________________________________________
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- NNAAMMEE
- fscmd - Set various parameters in the filesystem
-
- SSYYNNOOPPSSIISS
- ffssccmmdd -[mmMM] _s_i_z_e
- ffssccmmdd -[ffssllLLNNCCvv]
- ffssccmmdd -[wwWWxxXXyyzz]
- ffssccmmdd -[BBOOttDDRR]
- ffssccmmdd -ggeenneerriicc _a_r_g
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- _________________________________________________________________
-
- IINNTTRROODDUUCCTTIIOONN
- This command is used to set various kernel variables that
- control the filesystem cache, tracing and debugging output,
- and other features of the system. It is implemented using
- the Fs_Command system call.
-
- CCAACCHHEE SSIIZZEE
- The minimum and maximum number of filesystem blocks (4
- Kbytes each) in the main memory cache is set with the -m
- (minimum) and -M (maximum) arguments. Follow either of
- these with the number of 4-Kbyte blocks, ie. -M 512 means a
- max of 2 Megabytes in the cache.
-
- CCAACCHHEE CCOONNTTRROOLL
- --ff The entire contents of the cache gets written-back and
- then invalidated by specifying --ff.
-
- --ss [00|11]
- The background process that writes back dirty data from
- the cache can be disabled by specifying the ``--ss 00''
- flag. This should be done when patching a mounted
- filesystem or else bad internal structures will get
- pushed to disk. Enable the sync daemon with ``--ss 11''.
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- --ll [00|11]
- Biasing against ``large'' files in the cache is enabled
- with ``--ll 11'' and turned off with ``--ll 00''.
-
- --LL _s_i_z_e
- This sets what portion of the maximum cache size a file
- must occupy before it is considered a large file. For
- example a value of 8 would indicate that if a file is
- larger than 1/8 of the maximum cache size then it is
- considered a large file.
-
- --CC [00|11]
- Caching on diskless nodes can be disabled with ``--CC
- 00'', and turned back on with ``--CC 11''. This has to be
- done on a file server to affect its clients; use of the
- -C flag on clients will have no effect.
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- FSCMD User Commands FSCMD
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- --NN [00|11]
- The name cache on a diskfull node is disabled with ``--NN
- 00'' and enabled with ``--NN 11''.
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- --vv [00|11]
- The Virtual Memory cache of recently used program seg-
- ments is disabled with ``--vv 11'' (yes, 1), and enabled
- with ``--vv 00''.
-
- --bb _N Set the maximum number of block cleaner processes.
- This controls the amount of overlap during cache write-
- backs. 3 processes provides the most bandwidth, but it
- does load the server.
-
- --rr _N Set the read ahead distance (in 4K blocks). When a
- read on the cache is done, the transfer of N more
- blocks is initiated.
-
- CCAACCHHEE WWRRIITTEE BBAACCKK PPOOLLIICCYY
- Normally, dirty blocks in the file system cache are aged for
- at least 30 seconds before being written back. This gives
- the best performance, although alternate strategies can be
- tried out with the following flags. There are two write-
- back policies involved: the client's and the server's. Each
- of the flags below only affects the policy on the client or
- server on which it is invoked. For example the client could
- be using a write-through policy and the server a 30-second-
- delay policy. This would mean that client writes would not
- complete until the blocks have been written across the net-
- work into the server's cache, but the blocks would not be
- written back to disk until at least 30 seconds later.
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- --SS _s_e_c_o_n_d_s
- Set the cache write-back interval in seconds.
-
- --ww [00|11]
- Write-through caching is enabled with ``--ww 11'' and dis-
- abled with ``--ww 00''. With write-through, the write
- system call does not complete until the cache block is
- written back.
-
- --WW [[00|11]
- Write-back-on-close caching is enabled with ``--WW 11''
- and disabled with ``--WW 00''. With write-back-on-close
- the close system call does not complete until all of
- the file's dirty blocks are written back.
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- --xx [00|11]
- Write-back of temporary files can be set to delay as
- long as possible with ``--xx 11''. This is turned off
- with ``--xx 00''. Normally temporary files are files that
- are in the /tmp directory.
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- FSCMD User Commands FSCMD
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- --XX _d_i_r_N_u_m_b_e_r
- This identifies the temporary directory to the file
- system. _d_i_r_N_u_m_b_e_r should be the inode number of /tmp.
- Unfortunately, only one temporary directory is under-
- stood.
-
- --yy [00|11]
- Write-back-as-soon-as-possible caching is enabled with
- ``--yy 11'' and turned off with ``--yy 00''. With write-
- back-ASAP, the write system call completes immediately
- and the cache block is scheduled to be written out as-
- soon-as-possible.
-
- --zz [00|11]
- Write-back-on-last-dirty-block caching is enabled with
- ``--zz 11'' and turned off with ``--zz 00''. This policy
- only works on a server. It means the server writes
- back its blocks for a file after getting the last dirty
- block for the file from a client. For example, this
- policy combined with a write-back-on-close client pol-
- icy would mean that after a client closes a file, all
- of the files blocks are guaranteed to be on the
- server's disk.
-
- DDIISSKK LLAAYYOOUUTT
- --BB _s_k_e_w
- Set the block skew for disk allocation. Not supported
- in kernel yet.
-
- TTRRAACCIINNGG//DDEEBBUUGG FFLLAAGGSS
- There are several tracing/debugging flags that can have
- their value set via ffssccmmdd. Each flag expects a following
- integer on the command line that will specify the new value
- of the flag or trace level variable. FFssccmmdd prints out the
- old value of the flag as it changes it. Some of the flags
- are Booleans that are set with values of 1 for TRUE, and 0
- for FALSE.
-
- --OO The fsStats structure is zeroed out. This information
- is displayed with the fsStat program.
-
- --tt [00|11]
- Filesystem tracing is enabled with ``--tt 11''. This
- dumps internal events into a circular trace record.
- The trace gets printed via a special console key
- sequence, ``LL11--ff''.
-
- --DD [00|11]
- Cache consistency debug print statements are turned on
- with ``--DD 11'', and turned off with ``--DD 00''.
-
- --RR [00|11]
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- Read ahead tracing is enabled with ``--RR 11'' and turned
- off with ``--RR 00''.
-
- --ggeenneerriicc _a_r_g
- A generic hook for temporary file system operations.
- The result depends on arg.
-
- SSEEEE AALLSSOO
- fsStat, prefix, rpcCmd
-
- FFIILLEESS
- /local/diskcmds - Server local startup file
- /bootcmds - Network wide startup file
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- KKEEYYWWOORRDDSS
- debugging, trace, cache, write-back
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