On Fri, 10 Feb 2017, Jens-U. Mozdzen wrote: > Hello *, > > Zitat von Kai Krakow <hurikhan77@xxxxxxxxx>: > >[...] > >The hardware block size (aka sector size) is not what is meant here... > >You should use the biggest value. 8x512b fits into 4k. So bcache would > >simply use 4k as the block size and it just works despite the sectors > >being 512b. > > sorry for using confusing terms - yes, I was talking about sector sizes. > > >What I meant is "make-bcacke --block X". It defaults to X=512b. I think > >you may want to force it to 4k and see if your problem persists. > > I checked my various bcache backing stores and cache devices and got pretty > inconsistent values. Time to clean up. > > So trying to straighten things out, I started with a fresh backing device and > feel like something's broken here: > > - created a new RAID device, which has a sector size of 4096 per underlying > disks: > > myserver:~ # blockdev --getss /dev/md125 > 4096 > > - created the bcache super block > > myserver:~ # make-bcache -B --block 4096b /dev/md125 > UUID: 05d4d36a-ef17-4ecb-99d4-0a0eeec03941 > Set UUID: dd4165a9-47ca-4e35-9e7a-5968e1e40d92 > version: 1 > block_size: 8 > data_offset: 16 > myserver:~ # bcache-super-show /dev/md125 > sb.magic ok > sb.first_sector 8 [match] > sb.csum F4E616E067FA3C45 [match] > sb.version 1 [backing device] > > dev.label (empty) > dev.uuid 05d4d36a-ef17-4ecb-99d4-0a0eeec03941 > dev.sectors_per_block 8 > dev.sectors_per_bucket 1024 > dev.data.first_sector 16 > dev.data.cache_mode 0 [writethrough] > dev.data.cache_state 0 [detached] > > cset.uuid dd4165a9-47ca-4e35-9e7a-5968e1e40d92 > myserver:~ # ll /sys/fs/bcache/ > total 0 > drwxr-xr-x 7 root root 0 Feb 10 11:37 32c8c1f9-268c-4405-8fd7-ab9f5acbe3fb > --w------- 1 root root 4096 Feb 10 11:35 register > --w------- 1 root root 4096 Feb 10 11:35 register_quiet > myserver:~ # > > Why does it report 8 sectors per block? With 4k per sector, that'd be a block > size of 32k? Its in 512b units and 8*512=4096. Lots of things are in units of 512 even though your block size is 4096. Its correct, it just looks funny since you have 4k sectors. -- Eric Wheeler > > "myserver" has a running bcache setup in parallel, with the cache device > having a sector size of 512b (and bcache_super_show reports one sector per > block). Does this influence "make-bcache", although no cache is attached (and > the reported cset.uuid is different from the running bcache)? > > Regards, > Jens > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
