const char* get_device_name(unsigned id);
int _expand_slow_device(uint64_t min_size, PExtentVector& extents);
int _allocate(uint8_t bdev, uint64_t len,
const char* get_device_name(unsigned id);
int _expand_slow_device(uint64_t min_size, PExtentVector& extents);
int _allocate(uint8_t bdev, uint64_t len,