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Service, Support and Maintenance

No discussion of managing a hardware system would be complete without mentioning maintenance. At least, it shouldn't be! :^) I think enough about maintenance that I have a special section where I talk about it in some detail. Rather than repeat all of that information here, I will once again exploit the power of the web and simply refer you to there. Here I will only discuss maintenance as it applies specifically to RAID arrays.

That said, there isn't a lot to say. :^) RAID arrays don't generally require a lot in the way of regular preventive maintenance. You do need to maintain your server hardware, and the array should be part of that, but that's really all you need to do under normal circumstances: No special maintenance is required for RAID controllers or drives. At the same time, many high-end controllers do offer advanced maintenance features which can be useful, such as the following:

• Consistency Checking: This important feature will proactively check the data on a RAID array to ensure that it is consistent, meaning that the array data is correct and has not become corrupted. It is especially useful for RAID levels that use striping with parity, as it will check for any situations where the parity information in a stripe has become "out of sync" with the data it is supposed to match (which shouldn't happen in practice, but you know how Mr. Murphy works...) It will of course also correct any problems it discovers.
• Spare Drive Verification: If you are using hot spares, they will tend to sit there for weeks or months on end unused. This feature, if present, will check them to ensure they are in good working order.
• Internal Diagnostics: Some better RAID controllers may include routines to periodically check their own internal functions and ensure that they are working properly.

Now, let's take a look at service and support issues with RAID (I discuss these in more general terms in this troubleshooting section). In fact, there isn't anything different about service and support of RAID hardware than any other hardware. The difference is that RAID arrays are usually employed in servers used by many people, or in other critical situations which require a minimum of down-time. This means a failure that takes down an array can quickly cost a lot of money, lending an urgency to RAID array service that may not be present for other PCs.

There is no way to avoid down-time entirely unless you spend a truly staggering amount of money (and even then, you should "expect the unexpected".) If a failure occurs, you want to get it corrected as soon as possible, and that means you are reliant to some extent on whatever company is supporting your hardware. If uptime is critical to your application, then in addition to incorporating fault tolerance into your RAID setup, you should purchase an on-site service contract covering your system(s). Be sure to look at all the conditions of a service contract to be sure you understand what it covers--and what it doesn't. If you need immediate response in the event of a hardware fault be sure that the contract specifies that--you'll certainly pay more for it, but you have to weigh that against the cost of an entire company "waiting for the system to come back up".

Note: Another important issue to keep in mind when considering service and support of your RAID array, is that some arrays "insist" upon having failed drives replaced with identical models. You want the company that supplies you with hardware to be able to provide you with new drives of the appropriate type for the life of the array.

Next: Advanced RAID Features

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