This is actually an interesting thread considering we are covering an age old debate. I propose that we put some real thought into this question, it is too easy to simply repeat the age old answer that RAID 5 is better in every case.

In the name of performance the reality is that we IT professionals have wasted valuable resources for years, constantly over allocating to make up for various bottlenecks (system BUS, processor, RAM etc). We are seeing a dramatic surge towards consolidating systems that would previously be deployed as separate physical servers into one server machine using virtualization technology. This would NOT be feasible or acceptable in the Fortune 500 arena if hard drive technology was not up to par.

Based on technological advancements such as Serial Attached SCSI (SAS) drives with 15K spindles that are now available in capacities up to 450GB is there really a need to deploy RAID 5. Even for demanding applications such as MS SQL there are options such as 64 bit editions which would allow for much better performance. Apply limited resources to Memory instead of disk space. For single servers the real key is Hot spares!

Realistically speaking how many of you have ever run any diagnostic tools to determine the number of Disk I/O requests that your SQL server is generating? How many of you have ever worked with a SQL database larger than 100GB?

IF uptime is truly the desire then Direct Attached Storage (DAS) is a poor option anyway, when High Availability (HA) can be obtained by investing in a reasonably priced SAN. and even with that the host server would only need to run a RAID 1 array with a Hot spare!

I hear you man. I would not go nuts on a DAS, However, occationally I am called to setup several RAID servers connected to a SAN Box for Video post production for studios. These systems copy Gigabytes of data in the blink of an eye. I honestly don't see any bottlenecks or lags in the performance and the relaibility of RAID 5 makes everybody's job a lot easier.