09-23-2008
Linux FileSystem Internal Buffer size:
I know that Univ FileSystem stores all file data in the form of first few direct nodes followed by indirect nodes. But internally some systems implement where , a single block of 4096 isnt allocated alone a single block basis on physical drive, rather a large chunk of data is allocated and no. of blocks reside on it. This way they achieve efficieny in data read/write. This buffer contain blocks, can you anyone let me know the way to know that buffer size???? any ideas?
What is Fixed size disk block in Unix?
Last edited by GloriousDaisy; 09-23-2008 at 09:11 PM..
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RK(4) Kernel Interfaces Manual RK(4)
NAME
rk - RK-11/RK05 disk
SYNOPSIS
/sys/conf/SYSTEM:
NRK rk_drives # RK05
/etc/dtab:
#Name Unit# Addr Vector Br Handler(s) # Comments
rk ? 177400 220 5 rkintr # rk05
major device number(s):
raw: 15
block: 6
minor device encoding:
specifies drive: <rk_drive>
DESCRIPTION
Minor device numbers are drive numbers on one controller. The standard device names begin with ``rk'' followed by the drive number and
then the letter "h". The character ? stands here for a drive number in the range 0-7.
The block files access the disk via the system's normal buffering mechanism and may be read and written without regard to physical disk
records. There is also a `raw' interface which provides for direct transmission between the disk and the user's read or write buffer. A
single read or write call results in exactly one I/O operation and therefore raw I/O is considerably more efficient when many words are
transmitted. The names of the raw files conventionally begin with an extra `r.'
In raw I/O the buffer must begin on a word (even) boundary, and counts should be a multiple of 512 bytes (a disk sector). Likewise seek
calls should specify a multiple of 512 bytes.
DISK SUPPORT
The rk driver does not support pseudo-disks (partitions). Each file rk?h refers to the entire drive as a single sequentially addressed
file. Each drive has 4872 512-byte blocks.
It's not clear what one would do with one of these drives if one had one ...
FILES
/dev/rk[0-7]h block files
/dev/rrk[0-7]h raw files
/dev/MAKEDEV script to create special files
/dev/MAKEDEV.local script to localize special files
SEE ALSO
hk(4), ra(4), ram(4), rl(4), rp(4), rx(4), si(4), xp(4), dtab(5), autoconfig(8)
DIAGNOSTICS
rk%d: hard error sn%d er=%b ds=%b. An unrecoverable error occurred during transfer of the specified sector of the specified disk. The
contents of the two error registers are also printed in octal and symbolically with bits decoded. The error was either unrecoverable, or a
large number of retry attempts could not recover the error.
rk%d: write locked. The write protect switch was set on the drive when a write was attempted. The write operation is not recoverable.
BUGS
In raw I/O read and write(2) truncate file offsets to 512-byte block boundaries, and write scribbles on the tail of incomplete blocks.
Thus, in programs that are likely to access raw devices, read, write and lseek(2) should always deal in 512-byte multiples.
DEC-standard error logging should be supported.
A program to analyze the logged error information (even in its present reduced form) is needed.
3rd Berkeley Distribution August 20, 1987 RK(4)