SQL Server Clustered Tables versus Oracle Index Only Tables

A SQL Server clustered table and an Oracle index only table are essentially the same thing, a table that instead of being heap organised, is stored in sorted order. In the case of Oracle a B*Tree is used and a doubly linked list for SQL Server. But here is the interesting bit, in Oracle due to the expense of secondary index lookups, the use of index organised tables is the excpetion rather than the rule, however if you refer to this presentation from Kimberley Tripp, in SQL Server the use of clustered indexes is encouraged a lot more than their counterparts in Oracle. I can only assume that this is because SQL Server does not have an equivalent to Oracle's table lookup by rowid. In short this took me a bit by surprise.

Sane San . . . Sane Virtualization ?

James Morle published an article some time ago entitled "Sane SAN", it discussed the practicalities allocating database storage from a SAN. One of the points it touched on was the danger of being given an amount of storage without knowing how many physical spindles it was spread across. This was before virtualization took off, the problem being that there may be several layers of virtualization before you get down to the physical disks. For example, Hewlett Packard produce something called the Enterprise Virtual Array, this aggregates trays of storage into virtual arrays. With another product called SVM, which, off the top of my head stands for something like storage virtual manager, these virtual arrays can be pooled into virtual SANs.

On the subject of virtualization, the "Oracle Storage Guy" compares the price performance of Oracle RAC versus Oracle standard edition on clustered VMWare, with some caveats, clustered VMWare comes out the winner. This provides serious food for thought as to where it is best to carry out the clustering in the technology stack.