350 Nice

Right off the bat this SAN will host data files for FaxIt Nice. Possible expansion in the future may include e-mail and mysql storage but thats not a priority for now. Also because FaxIt Nice is a distributed application the filesystem will also need to support multiple initiators on each LUN. This immediately brings to mind Redhat Global Filesystem (GFS)
Our most likely OS will be Cent OS 5, as that is what i have decided to migrate to for all our servers in the future.

How many disks, what type of disks & what type of RAID?

After much deliberation i decided 8 SATA disks in a RAID 6 configuration should be plenty for us. Depending on the capacity of the disks we choose this will give us at least [disk size] * 6 usable capacity with the capacity of the other 2 disks providing the redundancy in the RAID array. Another option would be to sacrifice one more disk to have a hot spare. But with RAID 6 providing protection for up to 2 disk failures this is not a huge priority. Our colo is just a short drive away so I will just buy an extra disk to have on hand for a hot swap in the case of a failure.

Hold on a second…

A friend strongly advised that I use SAS or SCSI disks as the physical volumes for storage. At first I was shocked. “Is my plan for SATA not a good one?” I said to myself. But as i mulled it over i came to realize this. SAS/SCSI disks cost approximately 3 times as much for equivalent storage. SCSI is also 3 times faster. So both types have their pros and cons. After quite some time thinking about this and reading various articles on the web i came to the conclusion that SATA is just fine for our needs. Why? Well it all comes down to one main reason. We’re doing this mainly for redundancy and we dont have an unlimited budget. SATA disks are less expensive but also less reliable. With a RAID 6 setup if a disk fails we can replace it twice over before we have spent the same amount of money that we would have on a SAS disk. And because its RAID 6 we have an extra layer of protection while replacing a broken disk.

Kinks

I just heard from our ISP that the rack we reside in is using its max allocation of power. We’ll have to wait until we can move to a rack with a larger power supply. Hopefully this will take place soon as i am itching to get a better distributed storage solution than NFS setup.

Links

http://www.nas-san.com/differ.html
http://searchstorage.techtarget.com/originalContent/0,289142,sid5_gci935152,00.html
http://en.wikipedia.org/wiki/Hard_disk#Capacity_and_access_speed
http://www.pdl.cmu.edu/ftp/Failure/failure-fast07.pdf
http://www.equallogic.com/uploadedFiles/Resources/Technical_Bulletins/CB108_Reliability.pdf
http://www.enhance-tech.com/products/diskarrays/R8XP2000.html
http://www.sbei.com/files/OCSF%20White%20Paper.pdf