capacity issue?

[Duane Whitty]

On Sun, Jun 04, 2006 at 05:36:41PM -0400, Dave Stephens wrote:
> OS Version:  FreeBSD 6.1
> 
> It seems like the capacity of my drive is being reported incorrectly
> by df.  I'm not sure if this is a specific issue with the SATA drive
> or controller in the server, but I figured I would ask around.  There
> is only 1 physical drive in this server.
> 
> SATA Drive
> --------------------------------------------------------------------------------
> ad8: 286168MB <Seagate ST3300822AS 3.AAD> at ata4-master SATA150
> 
> SATA Controllers
> --------------------------------------------------------------------------------
> atapci1: <SiS 180 SATA150 controller> port
> 0xeff0-0xeff7,0xefe4-0xefe7,0xefa8-0xefaf,0xefe0-0xefe3,0xef
> 90-0xef9f irq 17 at device 5.0 on pci0
> ata2: <ATA channel 0> on atapci1
> ata3: <ATA channel 1> on atapci1
> atapci2: <SiI 3112 SATA150 controller> port
> 0xefa0-0xefa7,0xef8c-0xef8f,0xef80-0xef87,0xef88-0xef8b,0xe
> f60-0xef6f mem 0xfebfac00-0xfebfadff irq 17 at device 9.0 on pci0
> ata4: <ATA channel 0> on atapci2
> ata5: <ATA channel 1> on atapci2
> 
> Note that atapci1 is built onto the motherboard and doesn't seem to be
> supported by FreeBSD at this time (no HDDs can be found during install
> when they are attached to it.)
> 
> Mounting (dmesg)
> --------------------------------------------------------------------------------------------
> swapon: adding /dev/ad8s2b as swap device
> Starting file system checks:
> /dev/ad8s1a: FILE SYSTEM CLEAN; SKIPPING CHECKS
> /dev/ad8s1a: clean, 221765 free (2981 frags, 27348 blocks, 1.2% 
> fragmentation)
> /dev/ad8s4d: FILE SYSTEM CLEAN; SKIPPING CHECKS
> /dev/ad8s4d: clean, 9668716 free (980 frags, 1208467 blocks, 0.0% 
> fragmentation)
> /dev/ad8s4f: FILE SYSTEM CLEAN; SKIPPING CHECKS
> /dev/ad8s4f: clean, 51380314 free (18 frags, 6422537 blocks, 0.0% 
> fragmentation)
> /dev/ad8s3d: FILE SYSTEM CLEAN; SKIPPING CHECKS
> /dev/ad8s3d: clean, 28290946 free (32938 frags, 3532251 blocks, 0.1%
> fragmentation)
> /dev/ad8s3e: FILE SYSTEM CLEAN; SKIPPING CHECKS
> /dev/ad8s3e: clean, 9904253 free (1589 frags, 1237833 blocks, 0.0%
> fragmentation)
> /dev/ad8s4e: FILE SYSTEM CLEAN; SKIPPING CHECKS
> /dev/ad8s4e: clean, 37032718 free (998 frags, 4628965 blocks, 0.0%
> fragmentation)
> 
> output from df
> ---------------------------------------------------------------------------------
> Filesystem     Size    Used   Avail Capacity  Mounted on
> /dev/ad8s1a    494M     61M    394M    13%    /
> devfs          1.0K    1.0K      0B   100%    /dev
> /dev/ad8s4d     19G    497M     17G     3%    /home
> /dev/ad8s4f     98G    1.4G     89G     2%    /photo
> /dev/ad8s3d     57G    2.8G     49G     5%    /usr
> /dev/ad8s3e     19G     46M     17G     0%    /var
> /dev/ad8s4e     76G    5.0G     65G     7%    /www
> 
> last time i checked (just as examples)
> 98G - 1.4G is not 89G  (/photo)
> 57G - 2.8G is not 49G  (/usr)
> 76G - 5.0G is not 65G  (/www)
> 
> Can anyone tell me what's going on here?
> 
> Dave
> _______________________________________________

Hi,

Avail = (Size - "elbow room") - Used

The FFS algorithms need a little free space, about 5% I think,
in order to function efficiently.  This is also why you can
df report a disk more than 100% used.

Hth,

Duane Whitty
-- 
duane at dwlabs.ca