By Marc Staimer
On the other end, my distributed counterparts feel that they should also stripe the LUNs at the OS level because they have always done this.
What is the relative performance impact with this second layer of RAID? With the cache front ends of the storage devices being so large, will this affect me near-term or long-term as the storage workload increases?
Cache will have zero impact on throughput performance. In fact, if you turn off the back-end disk write cache, you can even improve the throughput. Cache is primarily for transactions and only improves performance if you have a high hit ratio which is a rarity when you have multiple servers/applications. The best way to use cache is to lock down part of it for database indexes and hot files. This has a real value for DBMS improved performance.
In general, the cache has nominal value for server-based striping.
As I stated in the beginning, there is no absolute answer to your question. It depends.
20 Oct 2005