Filesystem size and free space

[Andrei Kolu]

Ivan Voras wrote:
> Andrei Kolu wrote:
>   
>> Hi,
>>
>> due to migration from Windows Server 2003 NTFS filesystem to FreeBSD
>> 7.1Beta2 UFS+softupdates filesystem I encountered strange problem. NTFS
>> formatted filesystem seen in FreeBSD as read-only and exactly 500GB with
>> 28GB free space but after format to UFS disk shows up as 484GB and after
>> copying back files that was on same disk (from ntfs) UFS filesystem
>> shows that I got -33GB (minus?) of free space. What's wrong? Is UFS so
>> inefficient filesystem or it is a bug?
>>     
>
> UFS reserves a small percentage of the space for the superuser (root)
> utilities and also for performance benefits. "-33 GB" is telling you
> that you have used 33 GB of this reserved space, which isn't good if the
> file system is going to be used in a read-write environment. If the file
> system is going to be used read-only, you can safely ignore this;
> otherwise try never to use the reserved space. In particular, userland
> programs running under non-root user accounts will not see this reserved
> space and will get "out of disk space" errors when they try to add data
> to files in such a file system.
>
> You can lower the size of this reserved space with "tunefs -m" which
> will allow non-root users to access more space, but this isn't
> recommended. Either delete files or buy a bigger drive.
>
>   
So, I can say bye-bye to 50GB of space due to UFS filesystem features? 
IIRC then FreeBSD 4.x got 10% root reservation per filesystem and these 
days we got 1000 times bigger hard drives, do we need so much 
reservation (8% now I presume)? This filesystem would be read-only for 
users but writable to administrator to store large image files from 
other computers on network. If I understand correctly then this 
"reserved space" is used to avoid filesystem fragmentation. Can ZFS be 
more efficient, what if I create volumes per disk?

Andrei