Complete failure where the drive is no longer recognizable to your DVR, unrecognizable to a PC as well, and warrants replacement.These bad sectors can be physical which will warrant replacement of the drive, or read write errors which can be corrected with a simple drive format from with the DVR user menu. Bad sectors have developed on the drive and they are causing read/write errors, which essentially make the drive 'stuck' when it reaches a certain point or capacity.But when errors do happen, or the drive fails and drops out on the DVR you will get a error notice on your DVR stating there has been a hard drive failure. You simply don't know when it will happen. And an error occurring once on a particular brand and model of hard drive does not mean that manufacturer or model is bad. It is not possible to predict drive life, or prevent an incidence from occurring. Errors can occur on a new drive or one that has been functioning well for over 2 years. Taking in to consideration how fast they are moving, and that there is a small needle reading data from the drive platters, sort of like an old record player, it is possible to have a hiccup in the incredibly delicate process happening inside of your DVR's hard drive. Hard drives have spinning discs (or platters) inside which are constantly rotating at 5400rpm or 7200rpm. It is not uncommon to have a hard drive error on your Security DVR or Network Video Recorder (NVR).

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