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In just a few emails this afternoon we have defined the requirements for a >>>_*NEW*_<<< feature in ATA hard disk drives. The requirement of the >_*NEW*_< feature is that a drive keep a long term record of those sectors a host has "Marked As Having Bad Data". I don't know what to call this (bad, locked, come to mind but are not good terms). For now I will just use MAHBD to describe just sectors. The basic requirment seems to be this: A host needs to be able to select any sector and tell the drive to make it a MAHBD sector. The sector will remain a MAHBD sector until it is successfully written by the host or the MAHBD status is cleared by the host. Attempting to read a sector marked MAHBD shall result in an UNC (uncorrectable data error). In addition, MAHBD sectors shall not be affected or counted by SMART or other drive media scanning activities. Is this difficult to implement? Probably not. After all flash memory ATA devices (CF for example) keep a record of which sectors are currently "erased" and these devices have a command that returns the current "erased" status of a sector. I seems that we new a new command or commands to implement this feature: * a command to set MAHBD status for a sector. * a command to clear the MAHBD status for a sector. * a command to query the MAHBD status for a sector. * maybe a command to clear all MAHBD status. * maybe words in the ID data giving the maximum and current number of MAHBD sectors a drive supports. * probably also need a command to "lock" the MAHBD commands against improper use by a virus. There are lots of issues to consider, mostly interactions with other features: Host Protected Area, Security, SMART, etc. And then there are the nasty issues in the tech support area that goes something like this: "The drive was part of a RAID and never reported an error but now it is full of sectors with uncorrectable errors that were never reported by SMART. I want an RMA number and a new drive." THIS IS A NEW FEATURE. Never before have I heard anyone say that a drive needed to support the concept of a sector that the host wants to contain "bad data". I have never seen a drive that explicitly supported such a feature. Tradition is that a drive never has sectors with "bad data". Much effort goes into making hardware and firmware to insure a drive never has a sector with "bad data". Should I get a document number for this proposal or does someone else want to take it on? *** Hale Landis *** www.ata-atapi.com ***
