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Re: [Xen-users] LVM+Xen+FreeNAS possible?

To: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Subject: Re: [Xen-users] LVM+Xen+FreeNAS possible?
From: rajan chandi <chandi.rajan@xxxxxxxxx>
Date: Wed, 28 Oct 2009 12:39:02 +0530
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MogileFS takes care of replication, availability etc.

We are storing doc/pdfs.

e.g. first drive - /dev/sda3 - first MogilFS domU
       second drive - /dev/sda4 - second MogilFS domU

MogileFS will replicate the files across these drives. So, RAIDs are not needed.
We are not intending to update the files at all. So, don't need POSIX compliance.

There exist MogileFS-Clients for Java/Ruby and we are going to use that one.

The File Servers won't need the redundancy I think.
Let me know if you think otherwise!


On Wed, Oct 28, 2009 at 12:05 PM, Fajar A. Nugraha <fajar@xxxxxxxxx> wrote:
On Wed, Oct 28, 2009 at 1:23 PM, rajan chandi <chandi.rajan@xxxxxxxxx> wrote:

> MogileFS sounds to be a better option than FreeNAS due to scalability
> reasons.

Are you sure? From http://www.danga.com/mogilefs/

"MogileFS is not:

   * POSIX Compliant -- you don't run regular Unix applications or
databases against MogileFS. It's meant for archiving write-once files
and doing only sequential reads. (though you can modify a file by way
of overwriting it with a new version) Notes:
         o Yes, this means your application has to specifically use a
MogileFS client library to store and retrieve files. The steps in
general are 1) talk to a tracker about what you want to put or get, 2)
read/write to one of the places it told you you could (it'll pick
storage node(s) for you as part of its load balancing), using HTTP
         o We've prototyped a FUSE binding, so you could use MogileFS
without application support, but it's not production-ready.

Now if you simply want to use those 2x500GB disk as RAID0 and have
redundancy in another server with exact disk setup, I'd say you should
install crossover cable between the servers and install drbd.

I'm using drbd83-8.3.2-6.el5_3 from centos-testing. It works great in
general on my testing environment.
There were some issues earlier though (e.g. when using an earlier
version, one node panic when the other node restarts), so I'm still
rather reluctant to do widescale deployment. Oh and be SURE to have
network/serial console access ready (I use HP's ILO) if you plan on
deploying drbd :D


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