Re: lspv shows vpath?
From: Iain (iain_at_leamington-guide.com)
Date: 07/28/03
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Date: 28 Jul 2003 01:07:30 -0700
> > > > i did a lspv and there are vpaths shown. are these vpaths connected to
> > > > a SAN network?
> > > >
> > > >
> > > > smit, data path devices, display data path device status
> > >
> > > I should think you would be in a better position to know that than
> > > anyone else. Just because you have vpaths doesn't mean you have a
> > > SAN. You have an ESS. The connection from your server to the ESS is
> > > almost certainly either by SAN or by a direct SCSI connection.
> > >
> > > Iain.
> >
> >
>
> yup, when i do a lsdev -Cc disk , i had lots of IBM FC 2105F20. does
> that mean that we had lots of physical disks in our san?
The number of physical disks in the ESS that are visible to your
server should be equal to the number of vpaths the server has
configued.
Try the command lsvpcfg.
There could be many other disks on the SAN which your server cannot
see.
>
> also, when i do a lspv | grep 26
> i got the below
> 1) hdisk26 none None
> 2) vpath26 abcd1234 vg06
>
> lspv hdisk26 -> 0516-320 : Physical volume 0000000000000000 is not
> assigned to
> a volume group.
>
> lspv vpath26 -> info about the volume group
>
> on my other server with ssa, a lspv hdiskXX, gives info about the vg.
> my understanding is that insan environment, the access path uses is
> virtual path instead of the logical disk.
>
You almost certainly have a SAN (you could have point-to-point fibre
but not very likely). However, you are slightly mistaken about one
thing. Having vpaths is nothing to do with having a SAN. Vpaths come
from the SDD (Subsystem Device Driver) software which is installed on
the server and normally used with ESSs. It can be used if you have a
SAN, SCSI or point-to-point fibre connections. The vpaths give you
multiple routes to each ESS LUN, so if one path fails, you can still
access the disk via another path.
>
> > correct me if i am wrong.. the purpose of ESS, is for really fast
> > transfer. and therefore a SAN is almost inevitable.. with fibre
> > channel being used instead of SCSI Connection
I don't think that's quite right. In my experience, having switched
between the two a number of times, performance is quite similar on the
latest SCSI vs the latest fibre/SAN connections (at least when
connecting a server to an ESS).
What the SAN does give you is manageability. For example, the number
of servers you can connect to the ESS is not limited by the number of
adapters on the ESS. With a SAN you can have lots of servers
connected, all with multiple paths to the ESS. You can also reassign
storage to different servers, or to multiple servers, very easily.
Iain.
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