Creating sparse file on XFS and EXT3 has different results

[mani]

The ls uses st_size while du uses st_blocks.
So
st_size "file size in bytes"
st_blocks "number of 512 byte blocks allocated".
It depends upon the actual disk block size not the file system block size ..

try using the ls -ls it will give you both the o/p's .

Are you using the same hard disk with same disk block size ?


On Sat, Aug 6, 2011 at 9:51 PM, mani <manishrma at gmail.com> wrote:

> Dear Ashish,
>
> The ls uses st_size while du uses st_blocks.
> try using the ls -ls it will give you both the o/p's .
>
> Thanks
> Manish
>
> On Fri, Aug 5, 2011 at 7:45 AM, Ashish Sangwan <ashishsangwan2 at gmail.com>wrote:
>
>> I write 1 program to create sparse file which contains alternate empty
>> blocks and data blocks. For example block1=empty, block2=data, block3=empty
>> .....
>>
>> #define BLOCK_SIZE 4096
>> void *buf;
>> int main(int argc, char **argv)
>> {
>> buf=malloc(512);
>> memset(buf,"a",512);
>> int fd=0;
>> int i;
>> int sector_per_block=BLOCK_SIZE/512;
>> int block_count=4;
>> if(argc !=2 ){
>>         printf("Wrong usage\n USAGE: program absolute_path_to_write\n");
>>         _exit(-1);
>> }
>> fd=open(argv[1],O_RDWR | O_CREAT,0666);
>> if(fd <= 0){
>>         printf("file open failed\n");
>>         _exit(0);
>> }
>> while(block_count > 0){
>>         lseek(fd,BLOCK_SIZE,SEEK_CUR);
>>         block_count--;
>>         for(i=0;i<sector_per_block;i++)
>>         write(fd,buf,512);
>>         block_count--;
>> }
>> close(fd);
>> return 0;
>> }
>>
>> Suppose, I create a new_sparse_file using this above code.
>>
>> When I run this program, on ext3 FS with block size 4KB, ls -lh shows size
>> of new_sparse_file as 16KB, while du -h shows 8 kb, which, I think is
>> correct.
>>
>> On xfs, block size of 4kb, ls -lh shows 16KB but du -h shows 12kb.
>> Why are there different kinds of behavior?
>>
>> If I increase the block_count to be written so that a 200MB file is
>> created, on XFS du -h shows 187MB and on EXT3 it shows 101MB.
>>
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>>
>
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