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

Digimer linux at alteeve.com
Mon Feb 14 23:57:38 UTC 2011

On 02/14/2011 06:45 PM, Fajar A. Nugraha wrote:
> 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.

You can use DRBD as the PV for clustered LVM. :)

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