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VMWare, SANs and Replicating on the cheap

1 December 2006 One Comment

Yesterday, I attended the Virtualization Forum here in Sydney and thanks to Raghu Raghuram, VMware’s vice president of datacenter and desktop platform, my eyes were opened about not only the current but additionally the future possibilities of Virtualization. One of my biggest areas of interest in this regard is High Availability and Data Recovery. These two areas can be easily overcome if you throw enough money at it as nearly anything involving the words – “Cluster” or “High Availability” = SAN = $$$.

With VMware’s ESX 3.0 Enterprise Edition x 2 Servers connected to a SAN with Snapshots and Replication abilities – ooh, one is in heaven… but what if you can’t hit your boss up for the $100-200K required to migrate your 25 servers into one big, beautiful HA VMware cluster?

I went on a hunt this morning after the delicious solutions I saw yesterday and whilst nothing is downloaded, installed or tested, I did find some interesting starting points (some of which I had tried to find previously).

My starting points are:

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Openfiler is a powerful, intuitive browser-based network storage distribution. Openfiler, combined with the underlying Linux-based operating system, delivers file-based Network Attached Storage and block-based Storage Area Networking in a single framework. Openfiler is powered by rPath Linux. The entire software stack interfaces with third-party software that is all open source.

Networking protocols supported by Openfiler include: NFS, SMB/CIFS, HTTP/WebDAV, FTP and iSCSI (target). Network directories supported by Openfiler include NIS, LDAP (with support for SMB/CIFS encrypted passwords), Active Directory (in native and mixed modes) and Hesiod. Authentication protocols include Kerberos 5. Openfiler includes support for volume-based partitioning, Ext3, JFS, XFS and Reiserfs as on-disk native filesystem, point-in-time snapshots with scheduling, quota-based resource allocation, and a single unified interface for share management which makes allocating shares for various network file-system protocols a breeze.

An Openfiler based storage implementation can be configured to provide IP-based online volume replication for high-availability and data redundancy. All the tools to do this are entirely available as open source software as a part of the Openfiler distribution.

And as all good projects should have, there’s a Virtual Appliance for it on Sourceforge

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Openfiler uses DRDB for it’s one to one Data replication – As they say below “a network Raid-1″

DRBD is a block device which is designed to build high availability clusters. This is done by mirroring a whole block device via (a dedicated) network. You could see it as a network raid-1.

What is the scope of drbd, what else do I need to build a HA cluster?

DRBD takes over the data, writes it to the local disk and sends it to the other host. On the other host, it takes it to the disk there.

The other components needed are a cluster membership service, which is supposed to be heartbeat, and some kind of application that works on top of a block device.

Examples:

A filesystem & fsck.
A journaling FS.
A database with recovery capabilities.

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And last on my list of goodies Csync2

Csync2 is a cluster synchronization tool. It can be used to keep files on multiple hosts in a cluster in sync. Csync2 can handle complex setups with much more than just 2 hosts, handle file deletions and can detect conflicts. It is expedient for HA-clusters, HPC-clusters, COWs and server farms.

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Can’t wait to test some of the above! Will keep it posted.

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