Securepath vs LVM

[Shift Support]

Our environment is UX 11iv2 booting from an EVA3000. Two questions:

1)LVM seems to handle multiple paths to the same disk. So why install Securepath? Is it safe to run with LVM only?

2) If you install Securepath, Ignite-UX's recovery options do not work (make_net_recovery). System crashes when trying to boot from the restored disk. Anybody run into this?

[Sameer_Nirmal · Accepted solution]

1) You are right in saying LVM handles Multiple paths to the same disk as Securepath does.

In EVA there are 2 HSV controllers working in Active/Passive Mode. That means a Vdisk/LUN from you host will be active only on one of the controlles. Both controllers can't server the same LUN at the same time.

Now in case of one of the controllers failure, the LUN could be accessible from the another controllers. From HP-UX point of view , there has to be failover to the second controller path and it doesn't support the failover of its own ( unless you have LVM LV links). Hence SecurePath software is required to be installed on the host , so it will take care of the failover to another controller path and you don't have a situation as not able to access the LUN.

As far the failover to different path is considered , LVM could be used in place of SP. Remember SP provides you other feature apart from path redundancy is load balancing.
This load balancing ensures getting good I/O throughput as you are using both FPs on EVA controllers. Thats why HP recommends to use SP with EVA.

2) Youe second question is quite interesting.
I belive there should not be a problem using Ignite-UX with EVA for restored bootable LUN.

Can you provide more details about the crash??

[Shift Support]

Thanks for the information. The Ignite issue is documented here, unfortunately I did not see it we tried a test recovery.
If I read this correctly, if you put Securepath on then regardless or whether you boot from local or EVA disk your going to have problems with Ignite's recovery.

http://docs.hp.com/en/5990-8153/ch04s04.html
Compatibility


The Secure Path V3.0E is not supported for Ignite-UX type of installation or recovery
for the following two reasons:

When the Secure Path V3.0E is installed on a system, the hardware address of all EVA disk
luns change once the product is installed. During the recovery process, if LVM volume
groups exist on the EVA array, importing those volume groups may fail.
Further, if the boot disk resides on an EVA array, the system will fail to boot and is
most likely due to an LVM configuration failure panic.

The Secure Path V3.0E is not included in the install kernel and is not part of the
core HP-UX Operating System, so Ignite-UX is unable to support its use.

[Sameer_Nirmal]

Yes you are right.

I didn't know about the SP in-compatibility with Ignite-UX. SP V3.0E is providing EVA Boot and Dump support only. Let's hope to have solution on this from HP in near future.

[Shift Support]

Does anybody know if HP approves running UX without Securepath on an EVA, given the recovery option with securepath installed is a rebuild.

[Ranjith_5]

Hi Sandhu,

HP recommands running EVA with Securepath.

Regards,
Syam

[Shift Support]

Any ideas on how to do a recovery if you have installed securepath and Ignite make_net_recovery does not work?

[Leif Halvarsson_2]

Hi,

I run into a lot of trouble when trying to boot from SAN, using SP 3E. For the moment, i do SAN boot, using single path. It works OK (also together with Ignite) but, of course failower is not possible.

An (possible) alternative to SP/LVM is VxVM which , as I have understand, has multipathing built in. But, I am not sure if EVA is supported yet.

[Shift Support]

Seems like the best solution would be boot locally. Then you don't run into the recovery issue due to securepath.

Anybody using this solution?

[Bill Costigan]

You can use LVM on the eva3000 without securepath, however you cannot use the failover feature.

Typically, there are 4 paths (device files) for each LUN, 2 to one controller and 2 to the other. If you create an VG and only add two device files for the same controller LVM is happy. The two paths should be to the active controller not the passive one.

One problems is that once SecurePath is installed it will prevent you from doing this because it converts all the eva paths from sdisk to hsx devices. So it's all or nothing, unless someone knows how to tell secure path to ignore some devices.