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Re: Oracle ASM and RAW devices.

 
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tom quach_1
Super Advisor

Re: Oracle ASM and RAW devices.

Thank you all for the info.

question:
1-
would you want to use character device for the ASM disk group
/hpap/rdsk/hpap0 and not the block device /hpap/dsk/hpap0 ?
2-
Would anyone use this device /hpap/dsk/hpap0
to create volume group?

Thanks,
Tom
Sandman!
Honored Contributor

Re: Oracle ASM and RAW devices.

>question:
>1-
>would you want to use character device for the ASM disk group
>/hpap/rdsk/hpap0 and not the block device /hpap/dsk/hpap0 ?
>2-
>Would anyone use this device /hpap/dsk/hpap0
>to create volume group?

For the first question it depends on the application usage of data. Typically if the application reuses data then it is best to go with the block device file since data is buffered and cache hits would mitigate performance penalties. The rules for using raw over block device files and vice-versa remain the same.

No you would not use the virtual device file presented by AutoPath to create the VGs because this is storage side multi-pathing while LVM is host side multi-pathing software. You would create the VGs using LUNs presented by ioscan and vgextend the alternate links.

~hope it helps

Re: Oracle ASM and RAW devices.

Tom,

oops you're right - you would use the raw device special file for ASM, not the block.

HTH

Duncan

I am an HPE Employee
Accept or Kudo
tom quach_1
Super Advisor

Re: Oracle ASM and RAW devices.

Thank you Sandman and Duncan,

One more question on securepath
from securepath below, i have 2 path active/active
but when create vg group with these 2 active devices. It became active/alternate Link
why not active/active on vg group.

Thanks,
Tom



#autopath display

==================================================================
HPswsp Version : A.3.0F.02F.02F
==================================================================
Auto Discover : OFF
==================================================================
Array Type : VA
Array WWN : 060B-0000-151A-6F50
Path Verification Period : 00:10
==================================================================
Lun WWN : 6F00-0200-0000-0000-1D00-0000-0000-0000
Virtual Device File : /hpap/dsk/hpap0
Load Balancing Policy : Shortest Service Time
Lun Timeout : Infinite Retry (-1)
==================================================================
Device Path Status
==================================================================
/dev/dsk/c4t0d2 Active
/dev/dsk/c6t0d2 Active


--- Physical volumes ---
PV Name /dev/dsk/c4t0d2
PV Name /dev/dsk/c6t0d2 Alternate Link
PV Status available
Total PE 2559
Free PE 2309
Autoswitch On


Solution

Re: Oracle ASM and RAW devices.

Tom,

Secure Path and LVM are separate products with no rel knowledge of each other.

When you created the VG, you *could* have just added on of the didk devive special files, and Secure Path would still have managed failover to the other.

Of course another admin would need to know about Secure Path and run the commands to spot that the other device special file is pointing to the same actual LUN, and there's no harm in adding the alternate link as well. Secure Path should still be the component that manages failover to the other path as its further down the stack, but in theory LVM could as well - it's kind of a 'belt and braces' (is that 'belt and suspenders' in US english???) approach.

HTH

Duncan

I am an HPE Employee
Accept or Kudo
Sandman!
Honored Contributor

Re: Oracle ASM and RAW devices.

The feature that you are referring to is concerned with static or dynamic load balancing. The difference is that LVM is an example of an active/passive while Secure Path is an example of an active/active storage management system. LVM only provides static load balancing multiple paths while Secure Path provides dynamic load balancing over multiple paths (storage-side controllers). You can read more about it in the whitepaper below:

http://docs.hp.com/en/11822/storagemulti-pathing-HPUX-SG.pdf
tom quach_1
Super Advisor

Re: Oracle ASM and RAW devices.

Thank you very much for your helps!
Regards,
Tom