Hi everyone, After a few recent severe raid failures (one linux md, one 3ware), my understanding and fear about linux md is greatly increased. Single sector unrecoverable errors are doing us in! To alleviate these fears, we (my coworkers and I) believe we need to start a policy of conducting a 'background media scan' of the actual underlying physical devices in a raid 5. This is easily accomplished on the 3ware (it's built in), but we are struggling with linux md. A utility called SCU, http://www.bit-net.com/%7Ermiller/scu.html, will allow us to scan the media, and, if necessary, reassign the bad blocks. We have used this on scsi disks before, it seems to work, as a lowlevel tool. However! If two bad blocks are discovered on two different disks in the raid 5 (even if the bad blocks are in different stripes), we will be screwed, because the raid system will kick out the disk immediately when the first bad sector is found, and then reconstruction will fail when the second bad sector is found. screwed. Which brings me (finally) to my questions: 1) does linux md have a plan for integrating background media scanning and automatic sector reassignment like hardware solutions have? 2) how can we force (or manually perform) a stripe-wise resync? is it possible to take the raid offline completely, read the data with dd, compute the parity manually, reassign the bad block using SCU and rewrite the parity block with dd then put the raid online again? If #2 is possible, I'm sure a quick-and-dirty perl script could be created to do the work, which I'd be happy to do, if it's theoretically doable. Thanks, David - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
