VMTN Blog

[Update: see below]

Rich Bocchinfuso of GotITSolutions recently was at VMworld. He's been wondering about how the virtualization world attends to storage and I/O issues.

This [lack of familiarity] is understandable as the target audience for VMware had traditionally been the server engineering team and/or developers and not the storage engineers thus the probable lack of a detailed understanding of storage interconnects.

With VMware looking for greater adoption rates in the corporate production IT environment by leveraging new value propositions focused on business continuity and disaster recovery and host of others, Virtualized servers will demand high I/O performance characteristics from both an transaction and bandwidth perspective. Storage farms will grow, become more sophisticated and more attention will be paid to integrating VMware technology with complex storage technologies such as platform based replication (e.g. - EMC SRDF), snapshot technology (e.g. - EMC Timefinder) and emerging technologies like CDP (Continuos data protection).

A practical example of what I believe has been a lack of education around storage and storage best practice can be proven through the fact that I believe many VMware users are unaware partition offset alignment. Offset alignment is a best practice that absolutely should be followed, this is not a function or responsibility of VMware but it is an often overlooked best practice - (engineers who grew up in the UNIX world and are familiar with a command strings like “sync;sync;sync” typically align partition offsets but admits who grew up in the Windows world I find often overlook offset alignment unless they are very savvy Exchange or SQL performance gurus). Windows users have become accustomed to portioning using disk manager from which it is not possible to align offsets, diskpar must be used to partition and align offsets.

I would be interested in some feedback on how many VMware / Windows users did not do this during their VMware configuration of Windows VM install? Be honest! If you are not using disk par to create partitions and align offsets it means that we need to do a better job educating.

[Update: a commenter asked for more clarification of what in the world we're talking about. The definitive guide is Recommendations for Aligning VMFS Partitions, and the short answer is that you're fine as long as you're using VMware Infrastructure 3's VirtualCenter or the VI Client to create your VMFS partitions on your SAN. I blogged about this earlier and pointed to a nice article with some clarifying diagrams.]