Hi all! I would like to find a way for reducing resync / resilver time in case of disk replacement. Let's assume the following setup: 3x 1TB HDD -> dm-raid5 -> luks / lvm / ext4 / whatever AFAIU linux raid would resync the full 1TB of data regardless of whether only e.g. 500GB are actually in use or 1TB. Right? ZFS keeps track of blocks being used and TRIM'ed. So it would only resync 500GB of data in our first case above. This reduces the risk of losing all data caused by a second failure during resync by reducing the resync time by 50 percent. It would be really great to get similiar behaviour in linux raid. I'm currently trying to figure out how much work it would mean to implement this feature. I have never worked on linux raid source before so I may be completely wrong. Feel free to correct me. Linux raid currently syncs the whole disk space because it simply does not know which blocks are in use and which are not. Wouldn't it be relatively easy to keep track of block assignments and releases by TRIM just as ZFS does? Best regards Michael
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