Re: [linux-lvm] shared scsi, external storage, vtrack

[Michael Loftis <mloftis wgops com>]

--On August 28, 2005 4:27:57 PM +0300 Andrew Kornilov <hiddenman tpway com> 
wrote:

> Hi all.
>
> I have two identical servers with CentOS (aka RHEL4.1) and one external
> data storage Vtrak 8110
> (http://www.promise.com/product/product_detail_eng.asp?segment=VTrak&prod
> uct_id=135) which connected by two scsi cables to this servers. I need to
> setup something called "shared scsi" but i haven't any experience with
> such things. My main task is build HA system (Vtrak used for postgresql
> databases). Can anybody help me with docs, HOWTOs and other?

You'll need to do this one of two ways.  First (simplest, most catastrophic 
error-prone) either make *CERTAIN* the systems NEVER, EVER, simultaneously 
mount the storage volumes, or, use a multi-host disk filesystem such as 
Sistina's GFS.

outside of that there's nothing special to be done.  one host has to be 
passive/inactive at all times in the first option, the second option means 
you can't use LVM, since, unless I'm mistaken, LVM has *no* capability for 
shared storage mediums.

Now most of these products can also be setup so that each host has their 
own storage space, and therefore they work like any other disk subsystem, 
each host only sees what they can access, but it sounds like you're not 
interested in that.

In any case, with postgresql, you're not going to be able to share their 
backend storage, so you'll have to have two totally separate storage areas 
if you want two live servers, or, you have one live, and one passive 
standby.

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