I set up a ZFS system on a Linux x86 box.
[b]> 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[/b]
I did not make the export (vol01) into a volume. I know you can set default
blocksizes when you create volumes but you cannot make them exportable NFS
exports. Thus, I did not make the NFS exports into volumes and I did not
specify a blocksize on the NFS exports.
I am assuming that vol01 is using 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 while the biggest would be 128k
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
I do the following stat command:
[b]stat --printf "%n %b %B %s %o\n" * [/b]
The %b is the number of blocks used, %B is the blocksize.
The number of blocks changes after a few minutes after the file is created:
# stat --printf "%n %b %B %s %o\n" *
file.512 [b]1[/b] 512 512 4096
# stat --printf "%n %b %B %s %o\n" *
file.512 [b]1[/b] 512 512 4096
# stat --printf "%n %b %B %s %o\n" *
file.512 [b]1[/b] 512 512 4096
Q1) 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)??? This makes it seem that the minimum blocksize isn't 512 bytes but
1536 bytes.
Q2) Is there a way to force ZFS to use 512 blocksizes? That means that if a
file is 512 bytes in size or smaller, it should only use 512 bytes -- the
number of blocks it uses should be 1.
I don't know how to do that using the zpool or zfs options.
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