Multiple block device files for a single Virtual Disk in Linux

[arkie]

Hi all!

My EVA6000 disk array has a single Virtual disk (VDisk001) on it, but both my nodes running RHEL AS 4.0 (Update 4) are showing 4 device files (sdc,sdd,sde,sdf) all referring to the same Disk. How can I have exactly 1 device file for 1 Virtual Disk in Linux

[LucianoCarvalho]

Hi,


As your EVA has two controllers, and probably you have two san switches and one HBA on your server, you will see for devices because EVA6000 functions as active/active disks, that means that all paths to the virtual disk will be available simultaneously.
Even installing the secure path software, you will still see for devices on your server.

My opinion is that there is no way to have just one path on your server without loosing the "high availability" and "load balance" given by EVA of having multiple paths available for the same disk.

Best Regards

[arkie]

Hi Luciano

Glad so much to hear from U (so soon and unexpectedly). Pls. tell me how to get ober the situation. To summarize

1)My Oracle 10g RAC needs an OCFS partition
2)OCFS partition to store OCR and Voting Disk files
3)OCFS partition required to be in Shared Storage
4)A partition in Shared Storage has to be labelled first
5)That label is going to the (MIRROR) block devices
6) mount wants that LABEL should be assigned uniquely
7) Without OCFS, how do I proceed for Oracle 10g RAC

Pls. give me bit of more information

Once, I even suceeded by renaming the MIRROR device files - everything worked out well till the end.

But once I reboot the server(s), the block device names are retained and OCFS will fail to mount once again and ASM will fail and Oracle 10g RAC will be in a mess - I will be in a mess too - I am working for a customer.

Pls. Luciano give me some clues. Thanks in advance

Regards
Siddhartha

[LucianoCarvalho]

Hi,

I'm not an expert on Oracle, but I'm trying to nderstando why you had to rename the Mirror device file for Oracle to work.

Do you think that the has something related to the fact that the server is accessing your drives via 4 differente paths?

regards

[Ben Dehner]

It sounds like you are missing a component. As described, you are seeing multiple devices because of the multiple paths to the LUN. The problems is that, at your application layer (OCFS), the application doesn't know how to deal with multi-path IO.

I think what you're missing is a multi-path IO driver such as SecurePath that will handle the multi-path details and present a single block device to the application. This software will do things such as load-balancing and failover in case of a link failure.

[Rob Leadbeater]

Hi,

Assuming you're using Qlogic HBAs then you need to install the (HP) drivers that enable multi-pathing.

Which HBAs are you using specifically ?

Cheers,

Rob

[arkie]

Hi,

I am using HP StorageWorks FC2143 (HP Part No# AD167A). Yes I could get over the problem with SecurePath from HP. But again, another situation. When i configuring software RAID (Mirroring) at the time of OS Installation, SecurePath dosen't seem to have the same effect. Has Securepath got anything to do with Raid?

Furthermore, my /boot/efi is not mounting during system boot. I have to mount it manually. How can i assign a LABEL to my boot partition

[Rob Leadbeater]

Hi,

For the FC2143 you should use the drivers here:

http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareDescription.jsp?lang=en&cc=us&prodTypeId=12169&prodSeriesId=3185350&swItem=co-51731-1&prodNameId=1833540&swEnvOID=2027&swLang=8&taskId=135&mode=4&idx=0

which include Multipulse failover. You shouldn't need to use SecurePath.

These drivers only control the multiple paths to the physical disks. They have nothing to do with the software RAID.

Cheers,

Rob