What is LUN 0 (zero) in EVA ?

[Panuwat]

Hi all,
I don't understand about something in "EvaPerfUserGuide v1.8" manual.
=> "The EVA Performance Monitoring tools run only on Windows 2000 and later hosts. The tools require that LUN 0 (zero) of an EVA array be visible to the host operating system. The tools do not require an actual LUN be presented to the host operating system or be mounted as a drive letter."

But I think the EVA have not LUN 0. What is LUN 0 ?
Can I use EvaPerf on SMA ?
thank you.

[Uwe Zessin · Accepted solution]

The text is a bit confusing, because the EVA itself *always* presents a "LUN 0". But the host might not have access due to switch zoning. Unlike some other arrays, this is not a LUN of device type disk, which can confuse software and people.

It is used for 2 purposes:
1.) in-band management - the SMA needs a way to talk to the EVA, even when it is unconfigured

2.) most operating systems these days support quite a number (255) of disk LUNs on a fibre channel target (the EVA controller). Polling all LUN addresses would take quite some time. The 'fix' is to use a SCSI command REPORT LUNs. This is send against LUN 0 and the host receives a list of LUNs it has access to - no need to poll each address.

[S.Arunkumar]

Hi Panuwat

The EVA Lun0 is basically used for the virtualization part.You are not suposed to present this lun to any of the host.Whenever u Initialize an EVA it creates a LUN with LUN ID 0.It is not visible to you thro the command view.

It is a best practice to Load the EVA permoance monitoring tool in the initail stage of ur setup itself.Sine this particular product is having some bugs on it.The first time u configure the monitoring tool it discovers for the LUN 0 availability in the EVA and updates its database.In future for any queries related to the disk usage in the EVA,the monitoring tool contacts this LUN for the disk space usage.

It is not recomended to load any aditional s/w in the SMA .As the SMA is a customized Windows platform created only for the management purpose.Hp doesnot recomends even the service pack updates provided by the Microsof TEAM(as there are posibility of SMA crash).

Regards
S.Arunkumar

[Uwe Zessin]

No, the LUN 0 has nothing to do with the virtualization - it is a front-end communications device. You cannot present/unpresent LUN 0 to a host as an end-user - it is *always* presented, even when the EVA is not initialized.

EVAperf is automatically installed with CV-EVA V4. As you can install CV-EVA on the SMA, so you can EVAperf.

[Panuwat]

thank all.