Device Drivers character Device / block device ...?

[Vinayak_HPUX]

Q1] We format character device & used mount block device why this so. why we can not mount character device i.e. raw device.
Ex:
mkfs -F vxfs /dev/rdsk/disk1
but we can not
mount -F vxfs /dev/rdsk/disk1
We have to mount block device only
mount -F vxfs /dev/dsk/disk1
Why this so ....?

[Michal Kapalka (mikap) · Accepted solution]

hi,

you don't defined the mount point.

mount -F vxfs /dev/dsk/disk1 /some_mount_point

mikap

[Vinayak_HPUX]

Ya U r right correct one is
mount -F vxfs /dev/dsk/disk1 /mnt1
but my query is that why we can not mont raw /character device....?

[Michal Kapalka (mikap)]

hi,

you are creating filesystem structure on raw devices because it's faster as on the block devices.

check this link :
http://forums11.itrc.hp.com/service/forums/questionanswer.do?admit=109447626+1244110731714+28353475&threadId=878764

mikap

[Vinayak_HPUX]

Thanks lot for TOI

[Bill Hassell]

A block device points to a different driver (the major number in the device file), specifically one that always uses the buffer cache. This is used to increase performance by remembering previous blocks of data and recalling them from memory rather than disk. On the other hand, manipulating bits requires direct access to the disk so newfs, mkfs and pvcreate all require the raw (or character) device file. Only random access devices such as disks have a blocked and raw driver.

[Sajjad Sahir]

Dear friend

raw devices bypass the buffer cache and use DMA directly to/from the program's I/O buffers; they are normally restricted to full-sector transfers. Using raw devices generally will give you faster performance. Raw devices are used when making new filesystems, when checking unmounted filesystems, or for copying quiescent filesystems. The block devices are used to mount filesystems. Each disk has a block device interface where the system makes the device byte addressable and you can write a single byte in the middle of the disk.

thanks and regards

Sajjad Sahir

[Basheer_2]

www.unixguide.net

and click on the table to see the comparisons

[Vinayak_HPUX]

I got a solution
Thnkx