As part of the Pear installation guide, you will be presented with the "optional" step of running a File System Consistency Check. Although this step is optional for most users, it is highly recommended. This check will find and repair any pre-existing issues with your Hard Drive and file system that may cause problems during the Pearing process or which may be preventing your system from operating correctly.
Technical info (Only for those who are curious):
As hard drives are used, they age. The aging process results in a drive which overtime shrinks. The "shrinking" is the result of sections of the hard drive failing and being mapped off by the flash controllers as an area to avoid. This process is normal and is handled by the flash controllers which are designed to do as much. Over time enough blocks of memory are mapped off that the actual size of the Hard Drive changes significantly. This change is occurring at the hardware controller level and often is not communicated to, nor reflected by, the operating system which is also tasked to manage your storage. During the pearing process, we refresh you system and alert it to recognize the additional size of the TarDisk. If your existing SSD prior to the Pearing process had shrunk (via. the process described above), the newly peared Macintosh HD, will not resize correctly and will cause an error or not reflect the new size. Here is an example of an old MacBook being successfully repaired with FSCK -fy.