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External storage solution

Igor Smolyar
Occasional Visitor

External storage solution

Correctly me if I wrong in following statements:

1. Qlogic and emulex driver, which included in Linux kernel 2.6 tree, do not have failover/multipath capability.

2. In order to utilize failover/multipath capability I have to use drivers from Qlogic/Emulex or OEM site and enable failover/multipath in code or compilation.

3. Enabling failover/multipath in HBA driver is different between OEM vendors - HP, IBM, Sun etc

4. Linux device mapper with multipath, LVM and default Linux tree drivers for HBA devices, can be hardware independent solution for external storage with multipath and failover, right?

I am looking to implement general solution on Linux for external storage that can run on different hardware and provide multipath and failover capabilities. Possible options are to customize two drivers - qlogic and emulex and write some script to load these drivers in appropriate way. Or to work with Linux device mapper and LVM.

Thanks in advance
Tijl Dullers_4
Occasional Advisor

Re: External storage solution

Most of the times the big vendors such as HP and IBM are just using plain Qlogic or Emulex drives but are not always supporting the latest versions. Sometimes they indeed also OEM a given version of an Emulex or Qlogic driver as their own and change the name and version ifnromation for the driver.

When doing modifications to the Emulex / Qlogic drivers yourself you will loose all support for

1. Your system when it runs a supported version of Redhat e.g. RHEL

2. The storage vendor. They only support the entire storage system is all hosts are running officially supported drivers.

Igor Smolyar
Occasional Visitor

Re: External storage solution

Let's say I want to use all failover/multipath functionality of SAN solution, can I use drivers that distributed with RHEL? Or I must use OEM drivers that are different from default in kernel tree?

I think that working with Linux device mapper and LVM may solve many of hw compatibility related problems, what do you think?