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Re: [Linux-cluster] iSCSI GFS



isplist logicore net wrote:
My thread on SSI/VM/Sharedroot got me thinking because of the input some of you have put into the thread. There is some very valuable information in there. In fact, it got me wondering if my FC path might not be the greatest based on Gordan's (I think it was) input on the subject. I've also seen a few posts about iSCSI lately. Can anyone shed a little light on iSCSI and what I would need to give it a try.

iSCSI is just a connection protocol like Fibre Channel. They both do the same thing. iSCSI works over ethernet, while FC works over fibre. iSCSI is cheaper, and FC has traditionally been faster (although the point gets a bit moot with 1Gb and 10Gb ethernet as the storage stops being the bottleneck.

Can iSCSI be used to run a clustered LAMP setup which would be as flexible as FC for growth and management?

iSCSI and FC are equivalent. I personally prefer iSCSI because it's cheaper. In terms of features there isn't a great deal to choose between them.

Preferably, without having to buy any hardware to try it out :). I've already got FC gear but it looks like iSCSI is much easier to deal with. I read somewhere or had found, an open source iSCSI target driver no less.

Yes, iSCSI is now ISS pretty much end-to-end. But if you already have FC gear and if you have the required drivers for it, then there's no need to replace it.

Here is another thing you may find interesting:
http://sourceware.org/cluster/ddraid/
I stumbled upon it last night, and the ides seems great - network RAID 3.5 (n+1 like RAID 3,4,5). It seems to make sense for small-ish clusters, or situations where you are stacking RAID / cluster levels (e.g. RAID 3.5+3.5). But without the ability to dynamically add drives (like in standard MD software RAID) I'm not sure how useful it would be if you need a scaleable solution. It also wouldn't allow you to power down half of your cluster at off-peak times.

Gordan


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