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Space calculation

To: linux-xfs@xxxxxxxxxxx
Subject: Space calculation
From: Jan Derfinak <ja@xxxxxxxxxxxx>
Date: Fri, 19 Mar 2004 10:27:31 +0100 (CET)
Sender: linux-xfs-bounce@xxxxxxxxxxx
Hi.

I would like to ask how much space needs xfs for empty files?
I tested fix for bug #284. Good work, it works for me.
But I created file system on loop device with size 512MB and ran bonnie++:

# mkfs.xfs /dev/loop0 
meta-data=/dev/loop0             isize=256    agcount=8, agsize=16384 blks
         =                       sectsz=512  
data     =                       bsize=4096   blocks=131072, imaxpct=25
         =                       sunit=0      swidth=0 blks, unwritten=1
naming   =version 2              bsize=4096  
log      =internal log           bsize=4096   blocks=1200, version=1
         =                       sectsz=512   sunit=0 blks
realtime =none                   extsz=65536  blocks=0, rtextents=0

/tmp/bonnie++-1.02c/bonnie++ -d /mnt/mnt2 -u 0:0 -s 0 -n 500

Everything was fine, maximum alocated space was 29%:

/dev/loop0              519488    148032    371456  29% /mnt/mnt2

Then I created 500MB FS and I used modified bonnie according bug #284
comment #9.

# mkfs.xfs /dev/loop0
meta-data=/dev/loop0             isize=256    agcount=8, agsize=16000 blks
         =                       sectsz=512  
data     =                       bsize=4096   blocks=128000, imaxpct=25
         =                       sunit=0      swidth=0 blks, unwritten=1
naming   =version 2              bsize=4096  
log      =internal log           bsize=4096   blocks=1200, version=1
         =                       sectsz=512   sunit=0 blks
realtime =none                   extsz=65536  blocks=0, rtextents=0

Bonnie ended with this output:
# /tmp/bonnie++-1.02c/bonnie++ -d /mnt/mnt2 -u 0:0 -s 0 -n 500
Using uid:0, gid:0.
Create files in sequential order...Can't create file 0511996x7MCG: No space
left on device
Cleaning up test directory after error.

My question is why xfs (in this case) needs almost 4x bigger FS than is size 
of allocated space?

                                jan


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