[Linux-cluster] Cluster with shared storage on low budget

[Fajar A. Nugraha]

On Tue, Feb 15, 2011 at 6:39 AM, Nikola Savic <niks at logik-internet.rs> wrote:
>
>   Hello,
>
>   I need to setup cluster of 3 servers without separate storage device
> (SAN). Servers should join their local hard drives to create shared storage
> space. Every server in cluster has public (100Mbps) and private (1Gbps) NIC.
> Private 1Gbit network will be used for exchange of data (files) on shared
> storage. Additional request is that data on shared storage is highly
> redundant (complete mirroring is required).
>
>   I was wondering if following setup is possible and if anyone has any
> experience or comments on it:
> - Servers will export local disks of same size as iSCSI targets
> - Each server will access other's two servers disk over iSCSI initiator
> - CLVM will be used to set Volume Group on all 3 disks. In theory this VG
> will work on all servers, because they'll have access to all disks (either
> directly or over iSCSI).
> - CLVM will be used to create Logical Volume with mirroring option set to 3
> (-m 3). Since there are 3 disks (physical devices) forming VG, each server
> will have redundant copy of same data.
> - Created Logical Volume will have GFS2 on it, so that it can be shared by
> cluster.
> - Web server will store web application files (scripts and photos) on
> created GFS.
>
>   If it works, this setup should provide shared storage for cluster, built
> from already available local hard drives in servers forming cluster. By
> using LVM mirroring, each server will have the same copy of data, which
> should make cluster resistant to failure of any server.
>
>   I was wondering, is LVM smart enough to optimize reading and use local
> drive for read operations?

Can LVM mirror handle one server outage? Can it automatically pick the
difference when it's back on?
Looks like you'd better stick with drbd.

-- 
Fajar