On 12/28/2016 06:55 PM, Rick Stevens wrote: > On 12/28/2016 03:46 PM, Raman Gupta wrote: >> On 12/28/2016 06:35 PM, Rick Stevens wrote: >>> On 12/28/2016 03:14 PM, Raman Gupta wrote: >>>> On 12/28/2016 04:24 PM, Rick Stevens wrote: >>>>> On 12/28/2016 10:33 AM, Raman Gupta wrote: >>>>>> I would like to change the cache mode of an existing lvm cache volume. >>>>>> >>>>>> I see the following in the man page: >>>>>> >>>>>> `With the --cachemode option, the cache mode can be set when creating >>>>>> a cache LV, or changed on an existing cache LV.` >>>>>> >>>>>> However, it does not seem to work: >>>>>> >>>>>> # lvs -o cache_mode vg_raid10/lv_var >>>>>> CacheMode >>>>>> writethrough >>>>>> # lvconvert --cachemode writeback vg_raid10/lv_var >>>>>> # lvs -o cache_mode vg_raid10/lv_var >>>>>> CacheMode >>>>>> writethrough >>>>>> >>>>>> (Fedora 23, 4.8.14) >>>>>> >>>>>> The `lvconvert` command produces no output, and there is nothing in >>>>>> dmesg or the journal. >>>>> >>>>> Have you tried adding the "-v" or "--verbose" flags to see if there >>>>> is an issue? >>>> >>>> No change: >>>> >>>> # lvconvert --verbose --cachemode writeback vg_raid10/lv_var >>>> # lvs -o cache_mode vg_raid10/lv_var >>>> CacheMode >>>> writethrough >>> >>> Looking at the man page for lvconvert (at least under F24 and F25), the >>> "--type cache" flag is necessary to specify the "--cachemode writeback" >>> option: >>> >>> # lvconvert --verbose --type cache --cachemode writeback vg_raid10/lv_var >>> >>> You might have to specify the cache pool stuff as well. Not sure. I've >>> never done this. >> >> Yup, that's what I tried in the first place, but that doesn't work either: >> >> # lvconvert --verbose --type cache --cachemode writeback vg_raid10/lv_var >> --cache requires --cachepool. >> Run `lvconvert --help' for more information. >> >> Ok fine: >> >> # lvconvert --verbose --type cache --cachepool >> vg_raid10/lv_cache_pool_var --cachemode writeback vg_raid10/lv_var >> Executing: /usr/sbin/modprobe dm-cache-mq >> Executing: /usr/sbin/modprobe dm-cache-smq >> Cache is not supported with cache segment type of the original >> logical volume vg_raid10/lv_var. >> >> Argh. > > Did you follow the examples in "man lvmcache" when you set this up? > Something isn't right with the way the cache pool is set up. I did -- and the caching itself seems to be working just fine: # lvs -o lv_name,vg_name,pool_lv,cache_read_hits,cache_read_misses vg_raid10/lv_var LV VG Pool CacheReadHits CacheReadMisses lv_var vg_raid10 [lv_cache_pool_var] 96105 27540 > As I said, I've never done LVM cache stuff. I'd have to tinker with it > at home tonight (not risking my production machines here at the > office). Appreciate the help. Regards, Raman _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx
