Discussion:
HA-LVM vs CLVM
urgrue
2010-02-01 08:36:49 UTC
Permalink
Hello,
I need to set up a simple failover scenario. The idea is to have two
independent RHEL 5 systems on local disks, connected to a shared SAN.
The application is all on the SAN. Only one node is ever running at a
time. If the active node fails, the disk needs to be mounted on the
passive node and the application started.
Failover doesn't have to be fast or automatic, but it has to be simple
and reliable.
Depending on where I look, HA-LVM is sometimes recommended and other
times it's CLVM. Looking at red hat cluster it seems HA-LVM is a bit
overkill for my needs.
Any suggestions or other options?

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Matt Iavarone
2010-02-01 13:09:41 UTC
Permalink
I haven't used ha-lvm, but it doesn't seem to be overkill for your
needs. It looks tailored to your needs, in fact. The kb says that
ha-lvm is for failover volumes, those that will only be mounted on one
host (http://kbase.redhat.com/faq/docs/DOC-3068). So you don't need
to complicate things with a clustered file system.

On Mon, Feb 1, 2010 at 1:36 AM, urgrue <***@bulbous.org> wrote:
> Hello,
> I need to set up a simple failover scenario. The idea is to have two
> independent RHEL 5 systems on local disks, connected to a shared SAN.
> The application is all on the SAN. Only one node is ever running at a
> time. If the active node fails, the disk needs to be mounted on the
> passive node and the application started.
> Failover doesn't have to be fast or automatic, but it has to be simple
> and reliable.
> Depending on where I look, HA-LVM is sometimes recommended and other
> times it's CLVM. Looking at red hat cluster it seems HA-LVM is a bit
> overkill for my needs.
> Any suggestions or other options?
>
> --
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urgrue
2010-02-02 10:29:57 UTC
Permalink
It's a bit overkill in the sense that, as far as I have understood,
HA-LVM and CLVM imply the use of red hat cluster and its associated
components, luci, ricci, rgmanager, dlm, quorum and maybe fence device
configuration, etc.
All I really need is for the active node to mark the VG as "reserved"
one way or another and have other node(s) respect that and thus not
touch it unless forced to.
I would assume (hope) there is some simple solution that I'm just not
thinking of.



On Mon, 01 Feb 2010 06:09 -0700, "Matt Iavarone"
<***@gmail.com> wrote:
> I haven't used ha-lvm, but it doesn't seem to be overkill for your
> needs. It looks tailored to your needs, in fact. The kb says that
> ha-lvm is for failover volumes, those that will only be mounted on one
> host (http://kbase.redhat.com/faq/docs/DOC-3068). So you don't need
> to complicate things with a clustered file system.
>
> On Mon, Feb 1, 2010 at 1:36 AM, urgrue <***@bulbous.org> wrote:
> > Hello,
> > I need to set up a simple failover scenario. The idea is to have two
> > independent RHEL 5 systems on local disks, connected to a shared SAN.
> > The application is all on the SAN. Only one node is ever running at a
> > time. If the active node fails, the disk needs to be mounted on the
> > passive node and the application started.
> > Failover doesn't have to be fast or automatic, but it has to be simple
> > and reliable.
> > Depending on where I look, HA-LVM is sometimes recommended and other
> > times it's CLVM. Looking at red hat cluster it seems HA-LVM is a bit
> > overkill for my needs.
> > Any suggestions or other options?
> >
> > --
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> > unsubscribe mailto:redhat-list-***@redhat.com?subject=unsubscribe
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Matt Iavarone
2010-02-02 12:50:35 UTC
Permalink
On Tue, Feb 2, 2010 at 3:29 AM, urgrue <***@bulbous.org> wrote:
> It's a bit overkill in the sense that, as far as I have understood,
> HA-LVM and CLVM imply the use of red hat cluster and its associated
> components, luci, ricci, rgmanager, dlm, quorum and maybe fence device
> configuration, etc.
> All I really need is for the active node to mark the VG as "reserved"
> one way or another and have other node(s) respect that and thus not
> touch it unless forced to.
> I would assume (hope) there is some simple solution that I'm just not
> thinking of.
>
>
>
> On Mon, 01 Feb 2010 06:09 -0700, "Matt Iavarone"
> <***@gmail.com> wrote:
>> I haven't used ha-lvm, but it doesn't seem to be overkill for your
>> needs.  It looks tailored to your needs, in fact.  The kb says that
>> ha-lvm is for failover volumes, those that will only be mounted on one
>> host (http://kbase.redhat.com/faq/docs/DOC-3068).  So you don't need
>> to complicate things with a clustered file system.
>>
>> On Mon, Feb 1, 2010 at 1:36 AM, urgrue <***@bulbous.org> wrote:
>> > Hello,
>> > I need to set up a simple failover scenario. The idea is to have two
>> > independent RHEL 5 systems on local disks, connected to a shared SAN.
>> > The application is all on the SAN. Only one node is ever running at a
>> > time. If the active node fails, the disk needs to be mounted on the
>> > passive node and the application started.
>> > Failover doesn't have to be fast or automatic, but it has to be simple
>> > and reliable.
>> > Depending on where I look, HA-LVM is sometimes recommended and other
>> > times it's CLVM. Looking at red hat cluster it seems HA-LVM is a bit
>> > overkill for my needs.
>> > Any suggestions or other options?
>> >
>> > --
>> > redhat-list mailing list
>> > unsubscribe mailto:redhat-list-***@redhat.com?subject=unsubscribe
>> > https://www.redhat.com/mailman/listinfo/redhat-list
>> >
>>
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You don't need ricci or luci for either of these, but they do make it
easier to build and manage your clusters. You can use
system-config-cluster in their place.

You can use, I assume, use just ha-lvm and gfs2 without rgmanager or
cman, but how will you manage the filesystem if the node fails? Will
you manually mount it on your backup node? And there are many options
for a fence device. A red hat cluster using clvm and gfs2 is simple
and easy to manage.

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urgrue
2010-02-02 17:34:12 UTC
Permalink
On Tue, 02 Feb 2010 05:50 -0700, "Matt Iavarone"
<***@gmail.com> wrote:
> You don't need ricci or luci for either of these, but they do make it
> easier to build and manage your clusters. You can use
> system-config-cluster in their place.

I'll take a look at system-config-cluster. The manual just made it sound
like its kinda deprecated in favor of conga. And I'm not so crazy about
conga, it seems I'm able to get strange behaviour out of it even doing
the simplest things in the most pristine setups, which partly explains
my reluctance to use RHC in all its glory.

> You can use, I assume, use just ha-lvm and gfs2 without rgmanager or
> cman, but how will you manage the filesystem if the node fails? Will
> you manually mount it on your backup node? And there are many options
> for a fence device. A red hat cluster using clvm and gfs2 is simple
> and easy to manage.

Manual mount/activate on the backup node is fine and in fact required in
my case, for the same reason that it needs to be ext3 - my employer is
ultra-conservative. So I'm not really sure where all this leaves me...

The main fear, and the reason I don't want to just "not mount it" on the
passive node as suggested by others, is that some helpdesk newbie or
careless person goes and starts it on the passive node - very probably
destroying the whole thing. Without any measure in place to at the very
least produce a warning, it's a bit too plausible a scenario.

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Marti, Robert
2010-02-02 17:44:24 UTC
Permalink
Helpdesk newbie/careless people have root on the cluster?

Rob Marti

-----Original Message-----
From: redhat-list-***@redhat.com [mailto:redhat-list-***@redhat.com] On Behalf Of urgrue
Sent: Tuesday, February 02, 2010 11:34 AM
To: General Red Hat Linux discussion list; General Red Hat Linux discussion list
Subject: Re: HA-LVM vs CLVM

On Tue, 02 Feb 2010 05:50 -0700, "Matt Iavarone"
<***@gmail.com> wrote:
> You don't need ricci or luci for either of these, but they do make it
> easier to build and manage your clusters. You can use
> system-config-cluster in their place.

I'll take a look at system-config-cluster. The manual just made it sound
like its kinda deprecated in favor of conga. And I'm not so crazy about
conga, it seems I'm able to get strange behaviour out of it even doing
the simplest things in the most pristine setups, which partly explains
my reluctance to use RHC in all its glory.

> You can use, I assume, use just ha-lvm and gfs2 without rgmanager or
> cman, but how will you manage the filesystem if the node fails? Will
> you manually mount it on your backup node? And there are many options
> for a fence device. A red hat cluster using clvm and gfs2 is simple
> and easy to manage.

Manual mount/activate on the backup node is fine and in fact required in
my case, for the same reason that it needs to be ext3 - my employer is
ultra-conservative. So I'm not really sure where all this leaves me...

The main fear, and the reason I don't want to just "not mount it" on the
passive node as suggested by others, is that some helpdesk newbie or
careless person goes and starts it on the passive node - very probably
destroying the whole thing. Without any measure in place to at the very
least produce a warning, it's a bit too plausible a scenario.

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urgrue
2010-02-02 20:34:44 UTC
Permalink
On 02-Feb-10 18:44, Marti, Robert wrote:
> Helpdesk newbie/careless people have root on the cluster?
>

That's a bit of an oversimplification, but effectively, yes.
It's typical of large companies that take ITIL and all that a bit too
literally: the experts write the procedures the helpdesk newbies have to
follow (thus allowing the company to have fewer expensive experts and
more cheap newbies). That they regularly misread/typo/etc the procedures
is just "room for improvement" as opposed to "a fundamentally bad approach".

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m***@5-cent.us
2010-02-02 20:49:55 UTC
Permalink
> On 02-Feb-10 18:44, Marti, Robert wrote:
>> Helpdesk newbie/careless people have root on the cluster?
>>
>
> That's a bit of an oversimplification, but effectively, yes.
> It's typical of large companies that take ITIL and all that a bit too
> literally: the experts write the procedures the helpdesk newbies have to
> follow (thus allowing the company to have fewer expensive experts and
> more cheap newbies). That they regularly misread/typo/etc the procedures
> is just "room for improvement" as opposed to "a fundamentally bad
> approach".

*sigh*

And I think of h/a failover as an automatic process that occurs if the
heartbeat from the live server to the standby doesn't happen for perhaps
30 sec.

mark

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Zoran Salahovic Lendra
2010-02-03 09:36:10 UTC
Permalink
Heya,
I think that you shoud definitely use Conga to create your initial
configuratin files and test the cluster. It's easy and helpfull,... later
you can edit them and also use command line, scripts,... and so on. Take a
look at this small article to see what Conga provides, and also it's
architecture:
http://magazine.redhat.com/2007/03/19/teaching-your-cluster-and-storage-systems-to-dance-an-introduction-to-conga/


more info here:
http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.4/html/Cluster_Suite_Overview/s1-clumgmttools-overview-CSO.html#s2-conga-overview-CSO


you can try creating a resource and see if you like it.

"... shared resources to be used by high-availability services,... consist
of file systems, IP addresses, NFS mounts and exports, and user-created
scripts that are available to any high-availability service in the
cluster. "

About your main fear I would sugest a good User manuals for the people who
is going to work whit it,... And also Panadol hehe


Reagards,
Zoran




"urgrue" <***@bulbous.org>

Enviado por: redhat-list-***@redhat.com
02/02/2010 18:34
Por favor, responda a
General Red Hat Linux discussion list <redhat-***@redhat.com>


Para
"General Red Hat Linux discussion list" <redhat-***@redhat.com>, "General
Red Hat Linux discussion list" <redhat-***@redhat.com>
cc

Asunto
Re: HA-LVM vs CLVM






On Tue, 02 Feb 2010 05:50 -0700, "Matt Iavarone"
<***@gmail.com> wrote:
> You don't need ricci or luci for either of these, but they do make it
> easier to build and manage your clusters. You can use
> system-config-cluster in their place.

I'll take a look at system-config-cluster. The manual just made it sound
like its kinda deprecated in favor of conga. And I'm not so crazy about
conga, it seems I'm able to get strange behaviour out of it even doing
the simplest things in the most pristine setups, which partly explains
my reluctance to use RHC in all its glory.

> You can use, I assume, use just ha-lvm and gfs2 without rgmanager or
> cman, but how will you manage the filesystem if the node fails? Will
> you manually mount it on your backup node? And there are many options
> for a fence device. A red hat cluster using clvm and gfs2 is simple
> and easy to manage.

Manual mount/activate on the backup node is fine and in fact required in
my case, for the same reason that it needs to be ext3 - my employer is
ultra-conservative. So I'm not really sure where all this leaves me...

The main fear, and the reason I don't want to just "not mount it" on the
passive node as suggested by others, is that some helpdesk newbie or
careless person goes and starts it on the passive node - very probably
destroying the whole thing. Without any measure in place to at the very
least produce a warning, it's a bit too plausible a scenario.

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urgrue
2010-02-03 21:31:42 UTC
Permalink
Thanks, those links will be useful. I'm going to give RH cluster a try.
It seems to me that the HA-LVM implementation uses LVM tags and the
volume_list feature of LVM to implement the exclusivity I was looking
for. Clever.
If for some reason RH cluster won't work for me I can probably use the
same trick to create reasonably newbie-proof manual failover scripts.
Thanks to everyone for their help.


On 03-Feb-10 10:36, Zoran Salahovic Lendra wrote:
> Heya,
> I think that you shoud definitely use Conga to create your initial
> configuratin files and test the cluster. It's easy and helpfull,... later
> you can edit them and also use command line, scripts,... and so on. Take a
> look at this small article to see what Conga provides, and also it's
> architecture:
> http://magazine.redhat.com/2007/03/19/teaching-your-cluster-and-storage-systems-to-dance-an-introduction-to-conga/
>
>
> more info here:
> http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.4/html/Cluster_Suite_Overview/s1-clumgmttools-overview-CSO.html#s2-conga-overview-CSO
>
>
> you can try creating a resource and see if you like it.
>
> "... shared resources to be used by high-availability services,... consist
> of file systems, IP addresses, NFS mounts and exports, and user-created
> scripts that are available to any high-availability service in the
> cluster. "
>
> About your main fear I would sugest a good User manuals for the people who
> is going to work whit it,... And also Panadol hehe
>
>
> Reagards,
> Zoran
>
>
>
>
> "urgrue"<***@bulbous.org>
>
> Enviado por: redhat-list-***@redhat.com
> 02/02/2010 18:34
> Por favor, responda a
> General Red Hat Linux discussion list<redhat-***@redhat.com>
>
>
> Para
> "General Red Hat Linux discussion list"<redhat-***@redhat.com>, "General
> Red Hat Linux discussion list"<redhat-***@redhat.com>
> cc
>
> Asunto
> Re: HA-LVM vs CLVM
>
>
>
>
>
>
> On Tue, 02 Feb 2010 05:50 -0700, "Matt Iavarone"
> <***@gmail.com> wrote:
>
>> You don't need ricci or luci for either of these, but they do make it
>> easier to build and manage your clusters. You can use
>> system-config-cluster in their place.
>>
> I'll take a look at system-config-cluster. The manual just made it sound
> like its kinda deprecated in favor of conga. And I'm not so crazy about
> conga, it seems I'm able to get strange behaviour out of it even doing
> the simplest things in the most pristine setups, which partly explains
> my reluctance to use RHC in all its glory.
>
>
>> You can use, I assume, use just ha-lvm and gfs2 without rgmanager or
>> cman, but how will you manage the filesystem if the node fails? Will
>> you manually mount it on your backup node? And there are many options
>> for a fence device. A red hat cluster using clvm and gfs2 is simple
>> and easy to manage.
>>
> Manual mount/activate on the backup node is fine and in fact required in
> my case, for the same reason that it needs to be ext3 - my employer is
> ultra-conservative. So I'm not really sure where all this leaves me...
>
> The main fear, and the reason I don't want to just "not mount it" on the
> passive node as suggested by others, is that some helpdesk newbie or
> careless person goes and starts it on the passive node - very probably
> destroying the whole thing. Without any measure in place to at the very
> least produce a warning, it's a bit too plausible a scenario.
>
>

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Marti, Robert
2010-02-02 12:56:31 UTC
Permalink
Just don't mount it on the passive nodes until required.

Sent from my iPhone

On Feb 2, 2010, at 4:38, "urgrue" <***@bulbous.org> wrote:

> It's a bit overkill in the sense that, as far as I have understood,
> HA-LVM and CLVM imply the use of red hat cluster and its associated
> components, luci, ricci, rgmanager, dlm, quorum and maybe fence device
> configuration, etc.
> All I really need is for the active node to mark the VG as "reserved"
> one way or another and have other node(s) respect that and thus not
> touch it unless forced to.
> I would assume (hope) there is some simple solution that I'm just not
> thinking of.
>
>
>
> On Mon, 01 Feb 2010 06:09 -0700, "Matt Iavarone"
> <***@gmail.com> wrote:
>> I haven't used ha-lvm, but it doesn't seem to be overkill for your
>> needs. It looks tailored to your needs, in fact. The kb says that
>> ha-lvm is for failover volumes, those that will only be mounted on
>> one
>> host (http://kbase.redhat.com/faq/docs/DOC-3068). So you don't need
>> to complicate things with a clustered file system.
>>
>> On Mon, Feb 1, 2010 at 1:36 AM, urgrue <***@bulbous.org> wrote:
>>> Hello,
>>> I need to set up a simple failover scenario. The idea is to have two
>>> independent RHEL 5 systems on local disks, connected to a shared
>>> SAN.
>>> The application is all on the SAN. Only one node is ever running
>>> at a
>>> time. If the active node fails, the disk needs to be mounted on the
>>> passive node and the application started.
>>> Failover doesn't have to be fast or automatic, but it has to be
>>> simple
>>> and reliable.
>>> Depending on where I look, HA-LVM is sometimes recommended and other
>>> times it's CLVM. Looking at red hat cluster it seems HA-LVM is a bit
>>> overkill for my needs.
>>> Any suggestions or other options?
>>>
>>> --
>>> redhat-list mailing list
>>> unsubscribe mailto:redhat-list-***@redhat.com?
>>> subject=unsubscribe
>>> https://www.redhat.com/mailman/listinfo/redhat-list
>>>
>>
>> --
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Adam Miller
2010-02-02 13:48:15 UTC
Permalink
If you are going to have to mount it manually on the passive node when
a failure occurs, then why even worry about clustering? Why not just
have an ext3 volume on some shared storage?

You won't have to worry about locking and/or LWW because only one
machine will have it mounted at a time.

(This does sound like it needs to be a full blown RHCS deployment to
provide any realistic HA, but this ext3 and manual fail over should
"work")

-AdamM


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Mike Burger
2010-02-01 17:40:14 UTC
Permalink
> Hello,
> I need to set up a simple failover scenario. The idea is to have two
> independent RHEL 5 systems on local disks, connected to a shared SAN.
> The application is all on the SAN. Only one node is ever running at a
> time. If the active node fails, the disk needs to be mounted on the
> passive node and the application started.
> Failover doesn't have to be fast or automatic, but it has to be simple
> and reliable.
> Depending on where I look, HA-LVM is sometimes recommended and other
> times it's CLVM. Looking at red hat cluster it seems HA-LVM is a bit
> overkill for my needs.
> Any suggestions or other options?

NFS? If you've got an appliance, such as NetApp or something else that is
capable of hosting an NFS share, you could make use of NFS for this
purpose.


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