![]() ![]() That write operation is not complete until the data is properly written in a remapped location. If a bad block is encountered during a normal write operation, the controller marks that block as bad and the block is added to the “grown defects list” in the drive’s NVRAM. The data block containing the defect becomes unusable and must be “remapped” to another location on the drive. In addition, normal wear on a drive may result in an increase in media defects, or “grown defects,” over time. However, hard drives are not expected to be totally free of flaws. Hard drive media defects and other drive quality issues have steadily improved over time, even as drive sizes have grown substantially. It could also be the simple mirroring of data to maintain a complete copy that does not require parity calculations to reconstruct the missing elements. This redundancy may take the form of parity calculations that are dispersed throughout the array. RAID arrays are an industry standard for the protection of important data through redundancy. Please refer to the following extract from the Maintenance Best Practices for Direct-Attached SCSI Solutions document On the contrary Dell recommend doing at least one consistency check per month. Otherwise it is basically verifying that the redundant data on the drives is correct. However, the consistancy check is really only neccessary if you have recently replaced a drive in a raid. "I have not run into any issues with running the consistancy check on these types of servers. ![]()
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