![]() ![]() But you can, of course, deallocate the storage space occupied by bad sectors so that it is not used anymore. Image: Know SMART status using Disk Utility Use First Aid of Disk Utility to Repair the Hard Drive Also, Disk Utility may not support SMART on your external storage device. The information provided by the application is not comprehensive, but you can at least know whether your hard drive is OK or failing. Check Hard Drive's SMART Status Using Disk Utilityĭisk Utility uses SMART (Self-Monitoring, Analysis, and Reporting Technology) to check the status of your startup disk. Read on to know how to fix your hard drive containing bad sectors. Or, when your Mac freezes frequently or shuts down abruptly. The presence of bad sectors on your hard drive is detected when some of your files throw an error while you try to access them. You can’t read the data or write anything on to the bad areas through the read-write head. In case the bad areas of the platter contain stored data, then the data turns inaccessible. These damaged areas are called bad sectors. Generally, a hard drive gets scratches or dents due to jerks, mishandling, or ageing. Although a sector can go completely bad (with no amount of retries successfully able to read the sector), it's more than likely it will succeed eventually and force the exchange with a reserved sector - all behind the scenes for you.Physical damage to a Mac hard drive can’t be avoided given the electro-mechanical nature of the device. In other words, modern drives are very resilient to data loss and have provisions to keep you from losing your data. You can find out more about this paradigm by Googling "SSD over-provisioning" which explains the process in more detail. SSD use this principle as a part of its design since the amount of total space you have is actually quite a bit larger than what you can use. If you have problematic sectors, the controller will manage as I explained above, SMART will pickup the correction and relay it to the diagnostic tool. These tools will read every sector on the drive you're testing, exercising the ability to read from each sector. If you suspect that you have bad sectors, you can perform a full sector-by-sector diagnostic (via the Apple Hardware Test or other tools available for the Mac). Barring physical abuse of the hard drive, the first scenario is more likely to happen. ![]() ![]() Modern OSes, like Mac OS X, will see the message about the bad sector and manage it for you by marking it as a bad sector in the HFS+ (Mac OS X file system) for you. SMART will see that sector as bad and inform the host system for you. If the controller is unable to read from that sector at all, data in that sector is lost. ![]() SMART will also report the drive as failing soon. SMART will see that a reserved sector has been burned and decrement the counter that says how many reserved sectors are available. The next time you read from that "sector", the controller is intelligent enough to use the reserved sector again. If the controller sees that sector again and is still problematic, it will copy that sector's data to a reserved sector if it is finally able to read it and then "patch" that bad sector out in an internal table. If the controller reports difficulty reading a particular sector but finally succeeds after a couple retries, it will mark that sector in its log as experiencing an issue. SMART supported drives usually have a reserved bank of sectors. SMART attempts to address problems AS THEY OCCUR and predict problems BEFORE THEY OCCUR. The disk controller will check various sections of your disk, bad sectors being one of them, to determine the internal status (health) of the disk and take corrective action when available or log problems and relay them to the host computer as they occur. SMART operates actively (while you use your disk) and passively (in the background running diagnostics when you are not using your disk). As brightsplash indicated, Apple Hardware Test will query the SMART report for any troubles your drive(s) may be experiencing. Most BIOS or EFI in a system will query the SMART report from your drives and inform you of impending failure. You can use SMART to report any deficiencies in your HDD or SSD if you have the appropriate software. SMART is a part of the device (HDD or SSD) itself and runs independently of the operating system. SMART officially became a part of the ATA specification around 2004 and has been implemented in every drive since then. Variations of "Self Monitoring Analysis and Reporting Technology" (SMART) have been included in hard drives since the late 90s. I'd like to say that bad sectors have went the way of the Do Do, but they do exists, although modern (even those over a decade old) hard drives (and solid state drives) have provisions to make "bad sectors" a thing of the past. ![]()
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