Gary Mills wrote:
On Sun, Jul 10, 2011 at 11:16:02PM +0700, Fajar A. Nugraha wrote:
On Sun, Jul 10, 2011 at 10:10 PM, Gary Mills <mi...@cc.umanitoba.ca> wrote:
The `lofiadm' man page describes how to export a file as a block
device and then use `mkfs -F pcfs' to create a FAT filesystem on it.
Can't I do the same thing by first creating a zvol and then creating
a FAT filesystem on it?
seems not.
[...]
Some solaris tools (like fdisk, or "mkfs -F pcfs") needs disk geometry
to function properly. zvols doesn't provide that. If you want to use
zvols to work with such tools, the easiest way would be using lofi, or
exporting zvols as iscsi share and import it again.
For example, if you have a 10MB zvol and use lofi, fdisk would show
these geometry
Total disk size is 34 cylinders
Cylinder size is 602 (512 byte) blocks
... which will then be used if you run "mkfs -F pcfs -o
nofdisk,size=20480". Without lofi, the same command would fail with
Drive geometry lookup (need tracks/cylinder and/or sectors/track:
Operation not supported
So, why can I do it with UFS?
# zfs create -V 10m rpool/vol1
# newfs /dev/zvol/rdsk/rpool/vol1
newfs: construct a new file system /dev/zvol/rdsk/rpool/vol1: (y/n)? y
Warning: 4130 sector(s) in last cylinder unallocated
/dev/zvol/rdsk/rpool/vol1: 20446 sectors in 4 cylinders of 48 tracks, 128
sectors
10.0MB in 1 cyl groups (14 c/g, 42.00MB/g, 20160 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
32,
Why is this different from PCFS?
UFS has known for years that drive geometries are bogus, and just fakes
something up to keep itself happy. What UFS thinks of as a cylinder
bares no relation to actual disk cylinders.
If you give mkfs_pcfs all the geom data it needs, then it won't try
asking the device...
andrew@opensolaris:~# zfs create -V 10m rpool/vol1
andrew@opensolaris:~# mkfs -F pcfs -o
fat=16,nofdisk,nsect=255,ntrack=63,size=20000 /dev/zvol/rdsk/rpool/vol1
Construct a new FAT file system on /dev/zvol/rdsk/rpool/vol1: (y/n)? y
andrew@opensolaris:~# fstyp /dev/zvol/rdsk/rpool/vol1
pcfs
andrew@opensolaris:~# fsck -F pcfs /dev/zvol/rdsk/rpool/vol1
** /dev/zvol/rdsk/rpool/vol1
** Scanning file system meta-data
** Correcting any meta-data discrepancies
10143232 bytes.
0 bytes in bad sectors.
0 bytes in 0 directories.
0 bytes in 0 files.
10143232 bytes free.
512 bytes per allocation unit.
19811 total allocation units.
19811 available allocation units.
andrew@opensolaris:~# mount -F pcfs /dev/zvol/dsk/rpool/vol1 /mnt
andrew@opensolaris:~#
--
Andrew Gabriel
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