[Linux-cluster] Home-brew SAN/iSCSI

[Madison Kelly]

Andrew A. Neuschwander wrote:
> Madison Kelly wrote:
>> Hi all,
>>
>>   Until now, I've been building 2-node clusters using DRBD+LVM for the 
>> shared storage. I've been teaching myself clustering, so I don't have 
>> a world of capital to sink into hardware at the moment. I would like 
>> to start getting some experience with 3+ nodes using a central SAN disk.
>>
>>   So I've been pricing out the minimal hardware for a four-node 
>> cluster and have something to start with. My current hiccup though is 
>> the SAN side. I've searched around, but have not been able to get a 
>> clear answer.
>>
>>   Is it possible to build a host machine (CentOS/Debian) to have a 
>> simple MD device and make it available to the cluster nodes as an 
>> iSCSI/SAN device? Being a learning exercise, I am not too worried 
>> about speed or redundancy (beyond testing failure types and recovery).
>>
>> Thanks for any insight, advice, pointers!
>>
>> Madi
>>
> 
> If you want to use a Linux host as a iscsi 'server' (a target in iscsi 
> terminiology), you can use IET, the iSCSI Enterprise Target: 
> http://iscsitarget.sourceforge.net/. I've used it and it works well, but 
>  it is a little CPU hungry. Obviously, you don't get the benefits of a 
> hardware SAN, but you don't get the cost either.
> 
> -Andrew

Thanks, Andrew! I'll go look at that now.

   I was planning on building my SAN server on an core2duo-based system 
with 2GB of RAM. I figured that the server will do nothing but 
host/handle the SAN/iSCSI stuff, so the CPU consumption should be fine. 
Is there a way to quantify the "CPU/Memory hungry"-ness of running a SAN 
box? Ie: what does a given read/write/etc call "cost"?

   As an aside, beyond hot-swap/bandwidth/quality, what generally is the 
"advantage" of dedicated SAN/iSCSI hardware vs. white box roll-your-own?

Thanks again!

Madi