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If a single, standard LV is specified as the cache, use it directly instead of converting it into a cache-pool object with two separate LVs (for data and metadata). With a single LV as the cache, lvm will use blocks at the beginning for metadata, and the rest for data. Separate dm linear devices are set up to point at the metadata and data areas of the LV. These dm devs are given to the dm-cache target to use. The single LV cache cannot be resized without recreating it. If the --poolmetadata option is used to specify an LV for metadata, then a cache pool will be created (with separate LVs for data and metadata.) Usage: $ lvcreate -n main -L 128M vg /dev/loop0 $ lvcreate -n fast -L 64M vg /dev/loop1 $ lvs -a vg LV VG Attr LSize Type Devices main vg -wi-a----- 128.00m linear /dev/loop0(0) fast vg -wi-a----- 64.00m linear /dev/loop1(0) $ lvconvert --type cache --cachepool fast vg/main $ lvs -a vg LV VG Attr LSize Origin Pool Type Devices [fast] vg Cwi---C--- 64.00m linear /dev/loop1(0) main vg Cwi---C--- 128.00m [main_corig] [fast] cache main_corig(0) [main_corig] vg owi---C--- 128.00m linear /dev/loop0(0) $ lvchange -ay vg/main $ dmsetup ls vg-fast_cdata (253:4) vg-fast_cmeta (253:5) vg-main_corig (253:6) vg-main (253:24) vg-fast (253:3) $ dmsetup table vg-fast_cdata: 0 98304 linear 253:3 32768 vg-fast_cmeta: 0 32768 linear 253:3 0 vg-main_corig: 0 262144 linear 7:0 2048 vg-main: 0 262144 cache 253:5 253:4 253:6 128 2 metadata2 writethrough mq 0 vg-fast: 0 131072 linear 7:1 2048 $ lvchange -an vg/min $ lvconvert --splitcache vg/main $ lvs -a vg LV VG Attr LSize Type Devices fast vg -wi------- 64.00m linear /dev/loop1(0) main vg -wi------- 128.00m linear /dev/loop0(0) |
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| activate | ||
| cache | ||
| cache_segtype | ||
| commands | ||
| config | ||
| datastruct | ||
| device | ||
| display | ||
| error | ||
| filters | ||
| format_text | ||
| freeseg | ||
| label | ||
| locking | ||
| log | ||
| lvmpolld | ||
| metadata | ||
| mirror | ||
| misc | ||
| mm | ||
| notify | ||
| properties | ||
| raid | ||
| report | ||
| snapshot | ||
| striped | ||
| thin | ||
| unknown | ||
| uuid | ||
| vdo | ||
| zero | ||
| Makefile.in | ||