Long term availability of replacement HDDs for enterprise storage systems

Long term availability of replacement HDDs for enterprise storage systems

Modern hard drives, and especially enterprise hard drives, are inherently very reliable. Manufacturers such as Toshiba offer warranties of up to five years, which indicates their confidence in the products. Popular models such as Toshiba’s MG06 offer Mean Time To Failure (MTTF) figures of 2.5 million hours – a figure that has been increased from 2 million hours. In the real world, this means that in an installation of 1000 enterprise hard drives, users should expect only two or three drives to fail per year during the warranty period.

In enterprise installations IT professionals have to anticipate these occasional failures and have a plan for replacing the drives so that the overall integrity and performance of the storage system is not compromised.

Replacing drives is generally a simple matter as long as the originally used drive model is available, either because the IT department bought spares or it can still be sourced. The failed drive is then replaced by a new drive or replaced by the manufacturer with an RMA-equivalent model. In cases where production of the drive has ceased then the IT department will have to rely on any inventory available to be able to acquire a suitable replacement. Eventually any stock will eventually be exhausted. In fact, increasing drive reliability means that it is likely that stocks will become hard to find more often.

If a particular drive model is superseded and the new series is not a direct 1:1 replacement, then models of the older series will continue to be manufactured as spares, provided that there is sufficient demand. This is especially true for smaller storage capacities within a series. These models are then available with the extended lifecycle of the old series or as next generation “optimized low-end” models.

Eventually, this manufacturing of older models will cease at some time and the older models will no longer be available once any stock has dried up. Now the IT department is faced with the question: can I replace my old model with a new but slightly different model? The answer is "It depends".

In applications where hard drives or SSDs are “software-defined” managed as storage capacities, models with different characteristics can usually be used in parallel. Here it is important to ensure that the interface (usually a host bus adapter HBA) supports the new model. With RAID-based storage systems, replacement is more critical because RAID controllers aggregate a number of the same physical drives into one logical drive, assuming identical physical components.

Toshiba has performed some extensive testing to look at how different drives will perform as replacements in hardware RAID systems. To download your copy of the report, please click here:

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