SANtricity or Dell MDSM is complaining that there are unreadable or unrecoverable sectors detected on the storage array. You may see this the following error as well:
Failure Entry 1: USM_UNREADABLE_SECTORS_EXIST-Recovery Failure Type Code: 75
The following KB article from NetApp does a great job explaining what Unreadable Sectors are and how the system handles them: What is Unreadable Sector Management?
Generate a storage log bundle and open a technical support case so that the storage array can be diagnosed by support. In most cases, the system will flag the sectors as unreadable and not use them in the future. If there is a more systemic problem and the read errors migrate or there are large numbers of them, most likely a hard drive will need to be replaced or the volume will need be deleted, reformatted and reinitialized.