System/Library/PrivateFrameworks/MigrationKit.framework
MKStorage.h
@interface MKStorage : NSObject
@property (nonatomic) unsigned long long availableSpaceInBytes;
@property (nonatomic) unsigned long long availableSpaceInMegabytes;
@property (nonatomic) unsigned long long availableSpaceInGigabytes;
@property (nonatomic) unsigned long long availableSpaceInTerabytes;
- (id)init;
@end