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тАО05-28-2004 02:20 AM
тАО05-28-2004 02:20 AM
eva5000 OS Unit ID and LUN for and Open Vms cluster system
Also there is a note that say:
The OS Inuit ID must be unique in the host cluster.
My question are:
If a configure for example 10 virtual disk,
1-I have to assign differents OS Unit ID to each virtual disk, example from 1 to 10?
2-For the LUN also will be a good idea that be 1,2,4,5,6,7,8,9, and 10 respectively.
Also there is a note that say:
The OS Unit ID must be unique in the cluster host, really I am a little confuse,
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тАО05-28-2004 04:21 AM
тАО05-28-2004 04:21 AM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
in short form: 1=yes,absolutely! 2=it is ok that way
And now some details:
The 'OS Unit ID' and the LUN address are two different things.
The 'OS Unit ID' is a characteristic of a Virtual Disk (VD). When a VD is presented, OpenVMS takes this number and creates the device name from it. E.g. OS Unit ID = 4 gives device '$1$DGA4:', ID = 1357 gives '$1$DGA1357:'. The first part ('$1$DGA') is hard-coded in the OpenVMS device driver.
The LUN number is at which SCSI LUN address you map the Virtual Disk into the LUN adress space of the host. Each host has a different address space, so you can, e.g. map VD:'DATA01' to LUN #1 for host A and LUN #2 for host B. Assuming you have given the Virtual Disk the 'OS Unit ID':9 - on both hosts the resulting device will be '$1$DGA9:'.
You can leave the LUN address selection to the EVA and it will select a free number or you can assign them yourself (the EVA will not allow you to double-map two Virtual Disks to the same LUN address).
I hope it has become clear why you *MUST* make the OS Unit ID unique - otherwise an OpenVMS host is not able to tell devices apart. You risk crashing the system or corrupting your data.
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тАО05-28-2004 04:40 AM
тАО05-28-2004 04:40 AM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
I have another question:
How does OpenVms know whitch disk is going to be access by the cluster.
I mean if I present a LUN to a cluster, both system ;in my case are going to see the same LUN .
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тАО05-28-2004 05:08 AM
тАО05-28-2004 05:08 AM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
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тАО05-28-2004 05:13 AM
тАО05-28-2004 05:13 AM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
OpenVMS has a distributed lock manager (DLM) embedded. You can mount the disk on both members and access it from both members concurrently and directly. The file system is cluster-aware and ensures volume integrity with the help of the DLM. That is nothing new - it has worked since the mid-eighties (one of my previous employers implemented a cluster with shared disks in 1985) - only the disk technology was different.
This is a different working like a Microsoft Windows Cluster (MSCS) which works on a 'shared-nothing' principle. Both servers can 'see' the disk, but only one server will mount it and lock the other out with a 'SCSI reserve'.
Do you have any experience with clusters?
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тАО06-01-2004 03:36 PM
тАО06-01-2004 03:36 PM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
I good example of how this cluster technology is used today is Oracle Parallel server running on a 2-node cluster. Both nodes can see and access the database drives at the same time.
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тАО06-01-2004 09:18 PM
тАО06-01-2004 09:18 PM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
The SAN doesn't know or the node is a cluster member or not. Even for VMS it doen't matter. Actualy the message should be: The OS Unit ID should be unique on the whole SAN (per Fabrik ofcourse).
So if you're a VMS node in or without a cluster, the OS-U-ID should be unique because VMS is (as posted before) connecting to $1$DGA
AvR
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тАО06-02-2004 04:15 AM
тАО06-02-2004 04:15 AM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
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тАО06-05-2004 08:04 AM
тАО06-05-2004 08:04 AM
Re: eva5000 OS Unit ID and LUN for and Open Vms cluster system
The WWID of the LUN is a long string that uniqely identifies the VDISK.
The "LUN ID" is equivalent to the Dxx unit number in an HSG80 controller. This is the ID that AIX uses to identify the LUN. VMS ignores this ID number.
The OS unit ID is what VMS uses to present the LUN to the VMS OS. (Widoze uses this too)
If you used OS ID of 5, your VMS system would then see a $1$dga5 device.
As Uwe stated, this needs to ber unique for the cluster that it is being presented too. At the EVA controller level, I could have multiple disk with OS ID of 5. The EVA itself does not have a problem with this since it tracks by the LUN WWID. The VMS system would only see 1 $1$dga5 device that was the size of the first one presented to it.
Worry about your OS UNIT ID numbers. Let the EVA assign the LUN ID's as it will. They do not matter to the VMS system.
We also try to make these OS LUN ID's unique within the SAN fabric. We now have over 1500 LUNS active on our SAN fabrics. About 250 Servers using 48 storage array controllers.
Mike Naime
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тАО06-06-2004 01:27 AM
тАО06-06-2004 01:27 AM