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.
Regards,
Raman