17G File size limit?

[Theodore Ts'o]

On Fri, Sep 23, 2005 at 02:43:29PM -0700, Brandon Evans wrote:
> Hi everyone,
>   This is a strange problem I have been having.  I'm not sure where the 
> problem is, so I figured I'd start here.
> 
> I as having problems with Bacula stopping on 17Gig Volume sizes, so I 
> decided to try to Just dd a 50 gig file.  Sure enough, once the file hit 
> 17 gigs dd stopped and spit out an error
> 
> (pandora bacula)# dd if=/dev/zero of=bigfile bs=1M count=50000
> File size limit exceeded
> (pandora bacula)#
> 
> (pandora bacula)# ll
> total 20334813
> -rw-r--r--  1 root root 17247252480 Sep 23 00:44 bigfile

If you are using a 1k filesystem, then a file can consist of ten
direct blocks, plus 256 data blocks addressed via the indirect block,
plus 256*256 data blocks addressed from the indirect block, plus
256*256*256 data blocks from the triple-indirect block:

(10 + 256 + 256*256 + 256*256*256) * 1024 = 17247252480

Does that number look familiar?  So the problem is that you created
the file system using a 1k blocksize.  Filesystems with a 1k blocksize
are horribly inefficient for large files, and they max out at a little
over a little over 16 gigabytes.  (Note that 16 gigs is 17179869184
bytes, unless you are a disk drive company in which case your
marketing department calls it 17 gigs.  :-)

							- Ted








> -rw-r-----  1 root root   302323821 Sep 23 01:10 Default-0001
> -rw-r-----  1 root root   156637059 Sep 18 01:08 Diff-wi0001
> -rw-r-----  1 root root    46985831 Sep  6 19:38 Full-0001
> -rw-r-----  1 root root    47126293 Sep  7 14:39 Full-0002
> -rw-r-----  1 root root  2841621607 Sep 13 17:11 Full-wi0001
> -rw-r-----  1 root root     1584252 Sep 18 01:05 Inc-0001
> -rw-r-----  1 root root    97963834 Sep 14 01:05 Inc-wi0001
> 
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/hda2             9.7G  5.8G  3.4G  64% /
> /dev/hda1              99M   20M   75M  21% /boot
> /dev/hda4             102G  2.2G   94G   3% /home
> /dev/md2              221G   90G  120G  43% /mnt/storage
> none                 1014M     0 1014M   0% /dev/shm
> /dev/mapper/lvg01-coraid
>                       812G  693G  114G  86% /mnt/coraid
> 
> 
> 
> There are a few layers on this partation, so I figured I'd start at the 
> top with you guys and work my way down.  The partation this size limit 
> is on looks like so...
> 
> /mnt/coraid
> +--------+
> | Ext3   |
> +--------+
> | LVM 2  |
> +--------+
> | Raid 5 |
> +--------+
> 
> 
> So any one of these layers could be the problem.  I was able to create a 
> 100 Gig file on the /home partition, so perhaps ext3 is not the problem, 
> but I'm really not sure.
> 
> 
> The system is CentOs 4.1 running 2.6.13.2 (also tried 2.6.12.2)
> 
> Any insight would be great
> 
> -- 
> 
> Thanks,
>     Brandon Evans
> 
>  "I wouldn't recommend sex, drugs or insanity for everyone, but they've 
> always worked for me."
> -Hunter S. Thompson
> 
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