Hello Beard Developer, Looking at the error that you posted it looks like you had a parity error happen on the drive located Bus 1 Enclosure 2 Disk 8.  In most case your VNX 5300 will try to correct this error.  If you are seeing this error a lot on that drive, then that drive might be getting ready to fail.  If this is the first time that you received the error, then I would monitor the error to see if it returns on the same drive.  Please let us know if you have any other questions.
System Notification - VNX-5300.ced.local, ERROR, NaviEventMonitor Event Time: Jun  3 08:56:07 2019 Brief Description: CLARiiON call-home event number 0x956 Host SPB  Storage Array CKM00133400552  SPB  Device Bus 1 Enclosure 2 Disk 8  SoftwareRev 7.33.2 (0.51)  BaseRev 05.32.000.5.221  Description Parity Invalidated ExtCode1=438cf00; ExtCode2=13001000;.[IMAGE]All Disk Blink   Full Description: A CLARiiON call-home event with severity ERROR was received. Celerra Name:       VNX-5300.ced.local (10.158.253.53) Celerra Model:      VNX5300 Celerra Serial #:   CKM00133400552 NAS Version:        7.1.80-3   Severity:           ERROR Component:          CS_PLATFORM Facility:           NaviEventMonitor Message ID:         83224035341
Error VNX-5300