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SGI ONC3 NFS v2
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dist6.3
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cachefs.z
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cachefs
Wrap
Text File
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1996-11-21
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5KB
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133 lines
ccccaaaacccchhhheeeeffffssss((((4444)))) ccccaaaacccchhhheeeeffffssss((((4444))))
NNNNAAAAMMMMEEEE
cachefs - Cache File System Description
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
CCCCaaaacccchhhheeeeffffssss is a file system layered above other standard IRIX file systems.
It performs automatic local caching of data from one file system (called
the back file system) on another file system (called the front file
system). Any the following file systems may be used as the front file
system: _x_f_s and _e_f_s. Any of the following file systems may be used as
the back file system: _n_f_s, _n_f_s_3, _i_s_o_9_6_6_0, _c_d_f_s, _h_f_s, _k_f_s, and _d_o_s.
Data from the back file system is cached on the front file system when it
is first accessed. Subsequent accesses will retrieve the data from the
front file system. Consistency will be maintained with the back file
system in a manner similar to that used for NFS.
TTTTEEEERRRRMMMMIIIINNNNOOOOLLLLOOOOGGGGYYYY
ffffrrrroooonnnntttt ffffiiiilllleeee ssssyyyysssstttteeeemmmm
This is the local file system on which data is cached. The
supported back file system types are _x_f_s and _e_f_s.
bbbbaaaacccckkkk ffffiiiilllleeee ssssyyyysssstttteeeemmmm
This is the file system which contains the definitive copy of the
data. Data is retrieved from this file system and cached on the
front file system. Refer to _f_s_t_a_b(4) for a list of supported back
file system types.
ccccnnnnooooddddeeee
This is the internal data structure used by ccccaaaacccchhhheeeeffffssss to manage its
files. There is one _c_n_o_d_e for each open file. Each _c_n_o_d_e occupies
128 bytes on a 32 bit system and 256 bytes on a 64 bit system. In
addition, each _c_n_o_d_e points to a dynamically allocated area of 512
bytes containing metadata and attributes.
TTTTUUUUNNNNIIIINNNNGGGG
CCCCaaaacccchhhheeeeffffssss has a number of different tuning parameters, some of which are
supplied on the _m_o_u_n_t(1M) command (see _f_s_t_a_b(4)), some of which are
supplied via _c_f_s_a_d_m_i_n(1M), and some of which are kernel tuanbles
adjustable with _s_y_s_t_u_n_e(1M).
The kernel tunables are adjustable on a running kernel and control
readahead, asynchronous operations, and _c_n_o_d_e caching. The kernel
tunables are described below.
ccccaaaacccchhhheeeeffffssss____rrrreeeeaaaaddddaaaahhhheeeeaaaadddd
This controls the number of blocks to read ahead of the current
block being read. These will be read asynchronously. The size of
a block is whatever the preferred I/O size is for the front file
system.
PPPPaaaaggggeeee 1111
ccccaaaacccchhhheeeeffffssss((((4444)))) ccccaaaacccchhhheeeeffffssss((((4444))))
ccccaaaacccchhhheeeeffffssss____mmmmaaaaxxxx____tttthhhhrrrreeeeaaaaddddssss
This is the maximum number of asynchronous I/O daemons allowed to
be running per ccccaaaacccchhhheeeeffffssss mounted file system.
ffffiiiilllleeeehhhheeeeaaaaddddeeeerrrr____ccccaaaacccchhhheeee____ssssiiiizzzzeeee
This is the size in 512-byte units of the in-memory cache of file
header information (cached attributes and other metadata). This
number indicates the number of such headers retained after other
system internal data (e.g., the vnode) for a file has been
released.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
_c_f_s_a_d_m_i_n(1M), _f_s_t_a_b(4), _s_y_s_t_u_n_e(1M)
PPPPaaaaggggeeee 2222