default mkfs block size應該是多少

[watermelonyu]

我從某篇文章上看到........

Typically (in 11.x) when a vxfs FS is created even without the "-b" option it'll default to 8K block size

我不加block size 去makefs如下.....

#mkfs -F vxfs -o largefiles /dev/vg00/rlvol11

#fstyp -v /dev/vg00/rlvol11

f_bsize: 8192

# echo "8192B.p S" | fsdb -F vxfs /dev/vg00/rlvol11

bsize 1024

這兩個地方出現的值怎會不一樣.........

到底哪個才是真的



但是假如我我指定block size,下列兩個bsize就一樣了

#mkfs -F vxfs -o largefiles,bsize=8192 /dev/vg00/rlvol11

f_bsize: 8192

#echo "8192B.p S" | fsdb -F vxfs /dev/vg00/rlvol11

bsize 8192

[watermelonyu]

From the man page of mkfs_vxfs,

bsize=n

n is the block size for files on the file

system and represents the smallest amount of

disk space allocated to a file. n must be a

power of 2 selected from the range 1024 to

8192.



The default is 1024 for file systems

less than 8 gigabytes, 2048 for file systems

less than 16 gigabytes, 4096 for file systems

less than 32 gigabytes, and 8192 for larger

file systems.

[watermelonyu]

when you use fstyp -v to check the block size

of a file system, what field you need to look

at is f_frsize instead of f_bsize.

Because



1. fstyp(1m) command uses statvfsdev(3C) to obtain its data



2. From /usr/include/sys/_statvfs_body.h



struct __statvfs {



unsigned long f_bsize; /* preferred file system block size */

unsigned long f_frsize; /* Fundamental file system block size */



3. From kernel source



sp->f_bsize = VX_MAXBSIZE;

#define VX_MAXBSIZE 8192 /* largest block on any vxfs fs */



sp->f_frsize = fs->fs_bsize;

#define fs_bsize fs_dsk.fs_c.fsc_bsize

vx_u32_t fsc_bsize; /* size of blocks in fs */



Summary :

f_bsize: 8192 <---- f_bsize == VX_MAXBSIZE == 8192

f_frsize: 1024 <---- f_frsize == fsc_bsize == 1024 for this vxfs



Finally to summarise; I believe you need to be looking at the

f_frsize field of fstyp(1m) in order to determine the vxfs

block size correctly.