[linux-lvm] Two Plorilant servers (Redhat) trying to access a HP MSA1000

[linux-lvm] Two Plorilant servers (Redhat) trying to access a HP MSA1000

[Edgar Luna]

Hi everyone,

I have two servers with RedHat EL3 connected to an HP MSA1000. What I
want with this servers write/read the disks from the MSA1000.

I know that LVM is unaware of simultaneous access to one device, so I
tried to divide the storage of MSA1000 in two units (created via the ACU
application), that are seen by the RedHat servers as /dev/sda
and /dev/sdb. Then I created a Physical Volume for each one a Logical
Group and finally a Logical Volume for each of this.

I want an advice about this.
What would you do in my situation?
This works? I mean with this I can workaround the LVM 'problem' of
unaware of simultaneous access?
Is possible to access the Hard Drives in the MSA1000 directly from Linux
so I can make the LVM directly on disks?

I can't use GFS or that like because I can't afford to have only one
point of failure.

Thanks anyway.

-- 
Edgar Luna <eald@linuxuanl.org>
Linux UANL

Re: [linux-lvm] Two Plorilant servers (Redhat) trying to access a HP MSA1000

[Luca Berra]

On Thu, May 04, 2006 at 01:50:06PM -0500, Edgar Luna wrote:
>I have two servers with RedHat EL3 connected to an HP MSA1000. What I
>want with this servers write/read the disks from the MSA1000.
>
>I know that LVM is unaware of simultaneous access to one device, so I
>tried to divide the storage of MSA1000 in two units (created via the ACU
>application), that are seen by the RedHat servers as /dev/sda
>and /dev/sdb. Then I created a Physical Volume for each one a Logical
>Group and finally a Logical Volume for each of this.

could you clarify what your problem is?

>I want an advice about this.
>What would you do in my situation?
>This works? I mean with this I can workaround the LVM 'problem' of
>unaware of simultaneous access?

could you clarify what your problem is?

>Is possible to access the Hard Drives in the MSA1000 directly from Linux
>so I can make the LVM directly on disks?
no, you cannot, besides that, why did you buy an intellignet storage if
you only wanted a disk shelf?

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
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Re: [linux-lvm] Two Plorilant servers (Redhat) trying to access a HP MSA1000

[Edgar Luna]

On Sat, 2006-05-06 at 10:25 +0200, Luca Berra wrote:
> On Thu, May 04, 2006 at 01:50:06PM -0500, Edgar Luna wrote:
> >I have two servers with RedHat EL3 connected to an HP MSA1000. What I
> >want with this servers write/read the disks from the MSA1000.
> >
> >I know that LVM is unaware of simultaneous access to one device, so I
> >tried to divide the storage of MSA1000 in two units (created via the ACU
> >application), that are seen by the RedHat servers as /dev/sda
> >and /dev/sdb. Then I created a Physical Volume for each one a Logical
> >Group and finally a Logical Volume for each of this.
> 
> could you clarify what your problem is?
> 
Actually I have the *doubt* about the LVM capabilities. I know that LVM
can't control when trying to access the data simultaneously from many
servers. So I did this workaround of making two units in the MSA1000,
and making that each server access one of this units. But I want to
*know* if this will works, as far as I can see in this moment is working
but I want to know if what I did is wrong.

> no, you cannot, besides that, why did you buy an intellignet storage if
> you only wanted a disk shelf?
> 
Well, I didn't, but I guess they did that so they can change disks if
something wrong, and add more space later. Anyway I only was asked to
make the two proliant servers runs linux and write on the MSA1000 at the
same time. Then I realize that with LVM both servers can't access to the
same filesystem, so both can't use the whole space in the MSA1000. And
my problem begun, how to make this two Proliant server to write/read to
MSA1000.

Thanks.

Re: [linux-lvm] Two Plorilant servers (Redhat) trying to access a HP MSA1000

[Klaus Strebel]

Edgar Luna schrieb:
> On Sat, 2006-05-06 at 10:25 +0200, Luca Berra wrote:
>> On Thu, May 04, 2006 at 01:50:06PM -0500, Edgar Luna wrote:
>>> I have two servers with RedHat EL3 connected to an HP MSA1000. What I
>>> want with this servers write/read the disks from the MSA1000.
>>>
>>> I know that LVM is unaware of simultaneous access to one device, so I
>>> tried to divide the storage of MSA1000 in two units (created via the ACU
>>> application), that are seen by the RedHat servers as /dev/sda
>>> and /dev/sdb. Then I created a Physical Volume for each one a Logical
>>> Group and finally a Logical Volume for each of this.
>> could you clarify what your problem is?
>>
> Actually I have the *doubt* about the LVM capabilities. I know that LVM
> can't control when trying to access the data simultaneously from many
> servers. So I did this workaround of making two units in the MSA1000,
> and making that each server access one of this units. But I want to
> *know* if this will works, as far as I can see in this moment is working
> but I want to know if what I did is wrong.
> 
>> no, you cannot, besides that, why did you buy an intellignet storage if
>> you only wanted a disk shelf?
>>
> Well, I didn't, but I guess they did that so they can change disks if
> something wrong, and add more space later. Anyway I only was asked to
> make the two proliant servers runs linux and write on the MSA1000 at the
> same time. Then I realize that with LVM both servers can't access to the
> same filesystem, so both can't use the whole space in the MSA1000. And
> my problem begun, how to make this two Proliant server to write/read to
> MSA1000.
Hi Edgar,

i'd advise you to google up info about 'cluster shared storage' to give
your problem the right name ;-). I know that the LVM guys are working on
a cluster solution for LVM2, but i don't know the status and at least it
also depends on the filesystem you use, IMHO the OCFS2 of the current
kernel could be a solution for your problem, but there are several other
 solutions for this problem.

All in all, it's much more complicated than just creating to virtual
devices and put LVM on to of it ;-).

Ciao
Klaus

-- 
Mit freundlichen Gr�ssen / best regards

Klaus Strebel, Dipl.-Inform. (FH), mailto:klaus.strebel@gmx.net

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Re: [linux-lvm] Two Plorilant servers (Redhat) trying to access a HP MSA1000

[Luca Berra]

On Sat, May 06, 2006 at 12:11:21PM -0500, Edgar Luna wrote:
>On Sat, 2006-05-06 at 10:25 +0200, Luca Berra wrote:
>> On Thu, May 04, 2006 at 01:50:06PM -0500, Edgar Luna wrote:
>> >I have two servers with RedHat EL3 connected to an HP MSA1000. What I
>> >want with this servers write/read the disks from the MSA1000.
>> >
>> >I know that LVM is unaware of simultaneous access to one device, so I
>> >tried to divide the storage of MSA1000 in two units (created via the ACU
>> >application), that are seen by the RedHat servers as /dev/sda
>> >and /dev/sdb. Then I created a Physical Volume for each one a Logical
>> >Group and finally a Logical Volume for each of this.
>> 
>> could you clarify what your problem is?
>> 
>Actually I have the *doubt* about the LVM capabilities. I know that LVM
>can't control when trying to access the data simultaneously from many
>servers. So I did this workaround of making two units in the MSA1000,
>and making that each server access one of this units. But I want to
>*know* if this will works, as far as I can see in this moment is working
>but I want to know if what I did is wrong.
yes, this works, with your storage you can create units that behave just
like independent disks, so as long as you don't have two different
systems accessing the same unit that's ok.

>> no, you cannot, besides that, why did you buy an intellignet storage if
>> you only wanted a disk shelf?
>> 
>Well, I didn't, but I guess they did that so they can change disks if
>something wrong, and add more space later. Anyway I only was asked to
>make the two proliant servers runs linux and write on the MSA1000 at the
>same time. Then I realize that with LVM both servers can't access to the
>same filesystem, so both can't use the whole space in the MSA1000. And
>my problem begun, how to make this two Proliant server to write/read to
>MSA1000.
if you need both system to access both units at the same time, you have
two options
either use a shared filesystem like GFS, or simply use NFS to export the
area of the other server.

L.

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
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