topic Re: Device Drivers character Device / block device ...? in Operating System - HP-UX

Device Drivers character Device / block device ...?

Vinayak_HPUX — Thu, 04 Jun 2009 08:54:38 GMT

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 ....?

Re: Device Drivers character Device / block device ...?

Michal Kapalka (mikap) — Thu, 04 Jun 2009 09:09:42 GMT

hi,

you don't defined the mount point.

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

mikap

Re: Device Drivers character Device / block device ...?

Vinayak_HPUX — Thu, 04 Jun 2009 09:15:37 GMT

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....?

Re: Device Drivers character Device / block device ...?

Michal Kapalka (mikap) — Thu, 04 Jun 2009 09:20:19 GMT

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

Re: Device Drivers character Device / block device ...?

Vinayak_HPUX — Thu, 04 Jun 2009 09:37:51 GMT

Thanks lot for TOI

Re: Device Drivers character Device / block device ...?

Bill Hassell — Fri, 05 Jun 2009 00:01:39 GMT

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.

Re: Device Drivers character Device / block device ...?

Sajjad Sahir — Sat, 06 Jun 2009 12:39:44 GMT

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

Re: Device Drivers character Device / block device ...?

Basheer_2 — Sun, 07 Jun 2009 05:51:46 GMT

www.unixguide.net

and click on the table to see the comparisons

Re: Device Drivers character Device / block device ...?

Vinayak_HPUX — Mon, 31 Aug 2009 05:30:51 GMT

I got a solution
Thnkx