topic Re: xp128 2D+2D configuration. in Disk Enclosures

xp128 2D+2D configuration.

???_185 — Tue, 22 Nov 2005 02:57:41 GMT

this is one vgdisplay capture.as you can see one disk have three alternative disk.
does it required to configure 2D+2D?
I roughly understand i has been needed due to bcopy. but I don't know exactly.
I mean how does disk can split and mirror?

PV Name /dev/dsk/c12t0d1
PV Name /dev/dsk/c10t0d1 Alternate Link
PV Name /dev/dsk/c13t0d1 Alternate Link
PV Name /dev/dsk/c9t0d1 Alternate Link
PV Status available

Re: xp128 2D+2D configuration.

Torsten. — Tue, 22 Nov 2005 09:51:49 GMT

This are not alternative disks, but alternative pathes.
Your system is able to "see" a LUN thru 4 FC interfaces/pathes.
Have a look at the "xpinfo [-i]" output.

Re: xp128 2D+2D configuration.

Alzhy — Tue, 22 Nov 2005 13:40:22 GMT

It means your 2D+2D ldev/LUN is presented to 4 HBA's to your server.

With LVM it is shown as PVLINKS or Alternate Paths. Under this config - ONLY ONE active path to your LUN is active.

Same with VxVM DMP with the advantage of actually distributing load accross the 4 paths

Re: xp128 2D+2D configuration.

???_185 — Wed, 23 Nov 2005 01:24:32 GMT

So, why does it need 3 altanative path?
,for load distributing or bcopy ?

Re: xp128 2D+2D configuration.

Edgar_8 — Wed, 23 Nov 2005 03:22:48 GMT

Hi Zungwon,

Well the answer to that could be:
1. your IT shop standards state that LUNs must be distributed to more than 1 path
2. yes for load balancing
3. in cases where access to a LUN via the primary is inaccessible, the alternate path can be used

HTH