topic Re: Explain DSF in Operating System - HP-UX

Explain DSF

Abubakkar — Thu, 02 Dec 2010 09:08:02 GMT

what is difference between below dsf.
Persistent DSF Legacy DSF(s)
========================================
/dev/rdisk/disk3 /dev/rdsk/c0t0d0
/dev/rdisk/disk3_p1 /dev/rdsk/c0t0d0s1
/dev/rdisk/disk3_p3 /dev/rdsk/c0t0d0s3
/dev/rdisk/disk3_p2 /dev/rdsk/c0t0d0s2

Re: Explain DSF

Jayakrishnan G Naik — Thu, 02 Dec 2010 09:20:51 GMT

Hi Abu

This is the persistant dsf and legacy equivalents of an Itanium boot disk.

Its a physical disk so you dont have multiple legacy device files for the dsf.

disk 3 actually the dsf for disk c0t0d0

disk3_p1 is the EFI partition (FAT) which is represented by slice 1 in legacy i.e. c0t0d0s1

disk3_p2 (this is the pv in vg00)is the HPUX partition where the rootvg resides which is represented by c0t0d0s2
&
disk_p3 is the HPSP partition which is specifically to hold offline diagnostic tools.

If you have a lun with multiple paths you will have multiple legacy device names for each persistent dsf.

The persistant dsf is the default feature of hpux 11i V3 which provides inbuilt native multipathing. This helps to manage a single device name which actually maps all the device paths behind and manage failover automatically, gives flexibility to use some load balancing etc.

Hope this helps.

Thanks & Regards
Jayakrishnan G Naik

Re: Explain DSF

Jayakrishnan G Naik — Thu, 02 Dec 2010 09:28:56 GMT

Hi Abu,

I have a good document with me for understanding persistent device files -Native Multipathing. This will be very useful for you.

Attaching it here.

Thanks & Regards
Jayakrishnan G Naik

Re: Explain DSF

Ismail Azad — Thu, 02 Dec 2010 17:36:51 GMT

Hi,

Legacy DSFs are present only for the sake of backward compatibility and will be deprecated in the subsequent releases of HPUX. For those who have worked with 11iv2 the s1,s2 and s3 slices would help to familiarize in the sense that the disk would be capable of booting on an integrity server having the heart of the itanium architecture. Remember, that these are standard sections only on an integrity boot disk and not on PARISC servers. Adding to JGK the s3 slice also helps in giving certain cpu as well as memory diagnostics. The hpux.efi would typically be present on the first slice. You might also see the "dir" command work on these slices as they are similar to the FAT 32 filesystems.

Regards
Ismail Azad

Re: Explain DSF

P Arumugavel — Fri, 03 Dec 2010 10:13:36 GMT

Hi Abu,

Here ia na example I try to make you understand.

Legacy DSF:

You(Disk) have 4 routes (Multipath) to go to your office(Server). Office has 4 entrances(legacy dsf) to enter into.
But you can use a single route at a time and one entrance(primary dsf) to enter into office.
If one route (primary path) being used, got blocked, you will use a next route (alternative path) to travel to office.
And your entry will be through different entrance (DSF).
So you need to have 4 different gate pass(legacy dsf) to enter into your office.

Persistent DSF:

There are 4 routes, your team(Disk) used to go to office through different routes (Multipath) and meeting at same room(Server) at office.
So all four routes to office would be used simultaneously.
If one route got blocked, rest 3 routes would still be used to reach office till the problematic route get cleared.
But your team will enter into your office through a single entrance(persistent dsf). So you will have a single gate pass (persistent dsf).

rgds...