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Operating Systems Solaris Why does the # of blocks change for a file on a ZFS filesystem? Post 302283178 by sqa777 on Monday 2nd of February 2009 06:29:15 PM
Old 02-02-2009
Why does the # of blocks change for a file on a ZFS filesystem?

I created a zpool and zfs filesystem in OpenSolaris. I made two NFS mount points:

> zpool history



History for 'raidpool':
2009-01-15.17:12:48 zpool create -f raidpool raidz1 c4t1d0 c4t2d0 c4t3d0 c4t4d0 c4t5d0
2009-01-15.17:15:54 zfs create -o mountpoint=/vol01 -o sharenfs=on -o canmount=on raidpool/vol01
2009-01-15.17:20:13 zfs create -o mountpoint=/vol02 -o sharenfs=on -o canmount=on -o compression=lzjb raidpool/vol02



I did not make the mountpoints (vol01 and vol02) into volumes. I know you can set default blocksizes when you create volumes but you cannot make them exportable NFS exports.

I am assuming that vol01 and vol02 are variable blocksizes because I did not explicitly specify a blocksize. Thus, my assumption is that ZFS would use a blocksize that is the the smallest power of 2 and the smallest blocksize is 512 bytes.

I use the stat command to check the filesize, the blocksize, and the # of blocks.

I created a file that is exactly 512 bytes in size on /vol01 (the one without the LZ compression)

I do the following stat command:
stat --printf "%n %b %B %s %o\n" *

The %b is the number of blocks used.

The number of blocks changes after a few minutes after the file is created:

# stat --printf "%n %b %B %s %o\n" *
file.0 3 512 3 4096
file.512 1 512 512 4096
# stat --printf "%n %b %B %s %o\n" *
file.0 3 512 3 4096
file.512 1 512 512 4096
# stat --printf "%n %b %B %s %o\n" *
file.0 3 512 3 4096
file.512 3 512 512 4096

Why does the # of blocks change after a few minutes? And why are we using 3 blocks when the file is only 512 bytes in size (in other words, only 1 block is needed)???





 

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load_dat_font(3alleg4)						  Allegro manual					    load_dat_font(3alleg4)

NAME
load_dat_font - Loads a FONT from an Allegro datafile. SYNOPSIS
#include <allegro.h> FONT *load_dat_font(const char *filename, RGB *pal, void *param) DESCRIPTION
Loads a FONT from an Allegro datafile. You can set param parameter to point to an array that holds two strings that identify the font and the palette in the datafile by name. The first string in this list is the name of the font. You can pass NULL here to just load the first font found in the datafile. The second string can be used to specify the name of the palette associated with the font. This is only returned if the pal parameter is not NULL. If you pass NULL for the name of the palette, the last palette found before the font was found is returned. You can also pass NULL for param, which is treated as if you had passed NULL for both strings separately. In this case, the function will simply load the first font it finds from the datafile and the palette that precedes it. For example, suppose you have a datafile named `fonts.dat' with the following contents: FONT FONT_1_DATA FONT FONT_2_DATA FONT FONT_3_DATA PAL FONT_1_PALETTE PAL FONT_2_PALETTE Then the following code will load FONT_1_DATA as a FONT and return FONT_1_PALETTE as the palette: FONT *f; PALETTE pal; char *names[] = { "FONT_1_DATA", "FONT_1_PALETTE" } f = load_dat_font("fonts.dat", pal, names); If instead you want to load the second font, FONT_2, from the datafile, you would use: FONT *f; PALETTE pal; char *names[] = { "FONT_2_DATA", "FONT_2_PALETTE" } f = load_dat_font("fonts.dat", pal, names); If you want to load the third font, but not bother with a palette, use: FONT *f; char *names[] = { "FONT_3_DATA", NULL } f = load_dat_font("fonts.dat", NULL, names); RETURN VALUE
Returns a pointer to the font or NULL on error. Remember that you are responsible for destroying the font when you are finished with it to avoid memory leaks. SEE ALSO
register_font_file_type(3alleg4), load_font(3alleg4) Allegro version 4.4.2 load_dat_font(3alleg4)
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