mdadm

Q: MDADM mismatch_cnt > 0. Any way to identify which blocks are in disagreement?

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Sorry, ‘check’ does indeed write back to the array when it encounters an error – see https://www.apt-browse.org/browse/ubuntu/trusty/main/amd64/mdadm/3.2.5-5ubuntu4/file/usr/share/doc/mdadm/README.checkarray ‘check’ is a read-only operation, even though the kernel logs may suggest otherwise (e.g. /proc/mdstat and several kernel messages will mention “resync”). Please also see question 21 of the FAQ. If, however, while reading, a read error occurs, … Read more

Linux; What is stripe_cache_size and what does it do?

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from my understanding the stipe_cache_size is the number of stripe entries in the stripe cache. The stripe entries varies from systems to system but it is mostly controlled by the page size(default of 4096 bytes on linux systems)(https://github.com/torvalds/linux/blob/master/drivers/md/raid5.c#L73 , this file have all the logic of the stripe cache if you’d like to dig deeper) … Read more

mdadm mdadm: cannot open /dev/sda1: Device or resource busy

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do I need to…create the arrays for / and /boot while they are not mounted? Precisely. I hope you also realised that the old contents will be wiped in the process, so you might want to create a new array with one device missing (use mdadm –level=10 –raid-devices=8 –missing /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1 … Read more

How do I rename an mdadm raid array?

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Start with mdadm –detail /dev/md127: Version : 0.90 Creation Time : Wed Apr 13 20:03:21 2011 Raid Level : raid10 Array Size : 656765952 (626.34 GiB 672.53 GB) Used Dev Size : 437843968 (417.56 GiB 448.35 GB) Raid Devices : 3 Total Devices : 2 Preferred Minor : 8 Persistence : Superblock is persistent The … Read more

How to recover an mdadm array on Synology NAS with drive in “E” state?

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Just an addition to the solution that I found after I experienced the same issue. I followed dSebastien’s blog post on how to re-create the array: I found that that method of recreating the array worked better than this above method. However after re-creating the array, the volume was still not showing on the web … Read more