general SAN questions

[danlar]

Hello, I'm relatively new to the SAN world, aside from having set up a couple of XSANs. Those I did 'by the book', but now I have an EMC ax4-5i to work with and I'm not really sure how much of my XSAN knowledge applies here.

Is it normal to set up lots of LUNs of the same size and combine them into raid groups for each host, or would building single, large LUNs be more typical?

I sort of started throwing things together before I really thought it out, and I just created a few big LUNs, typically using every drive in a given chassis in a single RAID 5 block.

What's the better way to go here?

 

[danlar]

Ok that was probably not a good way to make my debut here. Let me go into a little more detail about what I'm trying to do.

I have an ax4-5i maxed out with 4 expansion chassis all loaded with 1TB SATA drives. This SAN is supposed to be the storage for all or at least most of the servers in a dell m1000e blade enclosure. At the moment, the only servers accessing this storage are a couple of web facing GIS applications.

One is a home grown app using open source tools including PostGIS (a version of PostgreSQL with a lot of GIS specific tools built in to it). This server will probably not be subject to exremely heavy loads- it's mainly intended to be used by our organization and a small group of trusted partners.

The other server feeds mapping data to other web servers over WMS. It has some image compression stuff going on to make serving the images more efficient.

What sort of configuration is going to work best for these servers? Do I want multiple striped LUNS to spread out the I/O is or a monolithic block of drives going to provide sufficient performance?

Where is the bottleneck in a system like this? The iSCSI connections are 1GB.

Any suggestions?

thanks

 

[kmcferrin]

Because you are using SATA the bottleneck will most likely be the drives themselves.

Before you can determine the best configuration you need to know what your utilization looks like. Is it more reads than writes or the other way around? Because it's images is it large blocks of sequential data? Is it all stored in the PostGIS database, and if so what are the performance tuning recommendations for that database files? What are the performance tuning recommendations for the log files? Do you know what kind of IOPS you will need to support the application, and whether or not your array will be able to provide it?

________________________________________
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[danlar]

Thank you- knowing what I don't know is actually very helpful in moving forward.