Internal Server Disks

Distributed storage (also known as Direct Attached Storage or DAS) still holds a great deal of corporate information today. The most common form of DAS, server internal storage, is still being purchased in large volumes today - though industry trends are clearly moving away from this traditional approach.

Internal Server Disks

Advantages

• Ease of purchase - Most server internal disk is purchased without any serious evaluation of the options or storage architecture planning, in a "want fries with that?" style add-on to the purchase of a server. Server vendors often encourage this approach, as it suits their interests to grow the value of each sale and keep storage captive to the servers.
• Low initial purchase cost - Adding a few extra GB of server disk looks inexpensive compared to the cost of establishing a new SAN infrastructure. When organisations are cutting back on capital expenditure, taking such a short-term view can seem like the easy option.

In recent years, the continuing rapid growth in data volumes has highlighted a number of problems inherent in this approach.

Disadvantages

• Limited scalability - Once the server is fully populated with drives, disk capacity cannot be further expanded. As a result servers must be upgraded more frequently than would otherwise be necessary, incurring hardware, downtime and people costs in the process.
• Limited availability - Without multi-host access to common storage there is little scope for the use of high availability techniques like clustering and fail-over to improve application uptime. Downtime-sensitive organisations often find this approach is a dead-end and must replace their storage in order to implement high availability systems.
• Poor utilisation - Surplus disk capacity on one server cannot be reassigned to another server, when that’s where it is most needed, resulting in costly wastage of storage space. Company-wide average utilisation figures for server internal disk rarely pass 50%, while utilisation figures for shared storage commonly exceed 85%.
• Higher TCO - A study by Merrill Lynch found that direct-attached storage had a 3-year TCO approximately 120% higher than that of SAN-attached storage, despite the much lower initial purchase cost. This was attributed largely to the higher storage management and backup costs for DAS, as well as lower average utilisation.

If you would like help to calculate the storage TCO for your organisation and prepare or evaluate a business case for networked storage, then Contact Us for no-obligation assistance.

Many organisations in the past have combined internal server disks with use of external disk arrays directly connected to individual servers. This approach has some advantages over internal server disks, but is still far from ideal.