diff between dsk & rdsk

[joseph51]

Can anyone explain me,what is the difference between dsk & rdsk in lvm.what is the use of this.where it is using exactly and when?

[Dennis Handly]

dsk is a block device and rdsk is a character device. The block devices go through the buffer cache. You want to use rdsk when using dd(1) to copy the raw disk.

[joseph51]

while we are creating,or extending the lv,or at the time of mirroring we are using this na,sometimes dsk & sometimes rdsk.But i didnot get the clear idea,where it to be use

[Venkatesh BL]

You would always use the 'block' device name for this purpose. Check the relevant man page.

[sujit kumar singh]

hi Binu,

dsk are the block devices and rdsk are the correspondig raw device files.
IO through the block device files takes palce in blocks whereas that thru the character or raw device files takes place thru characters.

we use the raw device files while using the very basic operations on devices that include the charater based IO on the device

we use raw device files of the disks /dev/rdsk/cxtydz while doing pvcreate,mkboot,vgcfgrestore,diskinfo
we use block device files of the disks while with commands as vgcreate,vgextend,vgimport,vgexport.

we use raw dev files of the LVs like /dev/vg02/rlvol2 while doing newfs,extendfs on them.
we use block dev files for LVs thst is /dev/vg00/lvol1 etc we use lvextend,lvsplit,lvmerge,lvlnboot,lvrmboot,mount,umount etc.


regards
sujit

[joseph51]

Thanks sujith

[Venkatesh BL]

Pls refer to http://forums11.itrc.hp.com/service/forums/helptips.do?#28 and assign points to those who helped!

[Dinesh kumar_5 · Accepted solution]

Hi Binu mathew

"dsk" is called block device file.when accessing device via block device file,system reads and write data through a BUFFER in memory,rather than transferring data directly to the physical disk.
advantage: improve input and output to physical disk


"rdsk" it is a character device file also called as raw device file.It transfer data to the device one character at a time.
Tape drives are typically accessed via character device file.

Hope this will help you.

[Avinash20]

Main difference: Writing via Buffer as stated above

[joseph51]

Thanks to all for your response