Using SANs and NAS

Appendix A. Disruptive Technologies

Today, one of the biggest decisions facing IT professionals and application designers is what kind of storage to use. Administrators choose between using a SAN for block-level I/O or using NAS for file-level I/O. Once that decision is made, your environment is locked into that storage resource for the life of the application or server.

One of the most revolutionary advances in computing is the separation of storage from the host processor. So why is it that the CPU is still running at about the same usage? In the world of SAN, we have increased throughput by bringing data through a much quicker medium. However, we have added the overhead of Logical Volume Managers and enterprise class filesystems. In the case of NAS, technology has moved the filesystem and volume management to an appliance; however connectivity is through the LAN. One type of I/O is replaced with another. An admin has now removed the CPU overhead of filesystem and volume management and replaced it with TCP/IP.

The innovations on the horizon will help remove these obstacles and bring to fruition the promises of SAN and NAS—allowing for emancipating storage from the CPU.

• The Direct Access File System (DAFS) is a type of network filesystem that requires a direct protocol for transport. It allows for direct memory-to-memory connection between host and storage, which allows for file-level I/O with direct attached performance.

• Virtual Interface (VI) is a direct access transport (DAT) ...