[linux-lvm] LVM/RAID again

[linux-lvm] LVM/RAID again

[Frank Lenaerts]

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I've been reading several LVM/RAID postings on this mailinglist to
find out if someone else is also having the same question as I have,
but this does not seem to be the case; I hope this is the right place
to ask this.

As LVM does not provide RAID1 (etc.) as VXVM does with its plexes, I
wanted to use LVM on top of the standard Linux metadevices
(RAID1). However, I wanted to do this for a cluster system using a
shared SCSI bus. I am aware of the fact that ownership of disks is
important, while something like LVM actually tries to abstract this
away, but I want to use LVM to be able to extend the filesystem, to
take snapshot backups etc.. The problem I currently face however, is
the fact that both nodes autodetect the metadevices and start syncing
the mirrors, independently of each other (I do not have the LVM and
cluster software installed on these machines yet). The synchronization
however, is initiated by the raidstart command, that is true (it is
not the detection itself which does this), but I wonder how I should
solve this problem. Below, some ideas that come to my mind:

- do not use LVM at all, just use the physical disks instead

- have two separate raidtab files where each of them is only "owned"
  by a single node (to prevent syncing problems) and only start the
  raid for a certain metadevice when a logical volume is imported on a
  node

What do you think about this?

-- 
frank.lenaerts@advalvas.be

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Re: [linux-lvm] LVM/RAID again

[Tim]

Having used and despised VxVM on Solaris before, and finding out about
Heartbeat since then, I'd look into attached enclosures shared
physically on a SCSI bus (there is an article in SysAdmin magazine that
I used for my starting point) and serial heartbeats across the nodes, if
the cluster is simple enough...  if not post to the linux-HA list :-)


Quoth Frank Lenaerts:
> I've been reading several LVM/RAID postings on this mailinglist to
> find out if someone else is also having the same question as I have,
> but this does not seem to be the case; I hope this is the right place
> to ask this.
> 
> As LVM does not provide RAID1 (etc.) as VXVM does with its plexes, I
> wanted to use LVM on top of the standard Linux metadevices
> (RAID1). However, I wanted to do this for a cluster system using a
> shared SCSI bus. I am aware of the fact that ownership of disks is
> important, while something like LVM actually tries to abstract this
> away, but I want to use LVM to be able to extend the filesystem, to
> take snapshot backups etc.. The problem I currently face however, is
> the fact that both nodes autodetect the metadevices and start syncing
> the mirrors, independently of each other (I do not have the LVM and
> cluster software installed on these machines yet). The synchronization
> however, is initiated by the raidstart command, that is true (it is
> not the detection itself which does this), but I wonder how I should
> solve this problem. Below, some ideas that come to my mind:
> 
> - do not use LVM at all, just use the physical disks instead
> 
> - have two separate raidtab files where each of them is only "owned"
>   by a single node (to prevent syncing problems) and only start the
>   raid for a certain metadevice when a logical volume is imported on a
>   node
> 
> What do you think about this?
> 
> -- 
> frank.lenaerts@advalvas.be



-- 
     "To be suspended from the legal profession is the moral equivalent of 
      being ostracized by child molesters."
                                                           --Ian Rowan

Re: [linux-lvm] LVM/RAID again

[Luca Berra]

On Wed, Mar 06, 2002 at 09:35:32PM +0100, Frank Lenaerts wrote:
> take snapshot backups etc.. The problem I currently face however, is
> the fact that both nodes autodetect the metadevices and start syncing
> the mirrors, independently of each other (I do not have the LVM and
...
> - do not use LVM at all, just use the physical disks instead
this is not an lvm problem but an md one
list is linux-raid@vger.kernel.org

> - have two separate raidtab files where each of them is only "owned"
>   by a single node (to prevent syncing problems) and only start the
>   raid for a certain metadevice when a logical volume is imported on a
>   node
get rid of raidstart and raidtab and use
mdctl from neil brown
http://www.cse.unsw.edu.au/~neilb/source/mdctl/
also be sure you are not using raid autodetection


L.

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