Datastore unavailable for heartbeat

Hi for all,

we have this issue with our infrastructure.
with this configuration:

- DellEMC-ESXi-6.7U2-13006603-A00 (Dell)
- SERIAL: [personal information removed by Mod]
- BIOS 2.2.9
- MODEL PowerEdge T640
- 2 DATASTORE: TYPE VMFS6
- Raid 5 configuration

This is a Vmware host that include a different vm's.
Currently some vm's are unacessible because having a dependencing file from datastore 1 that result ko.

What kind of problem does the disk have ?
is it in need of replacement ?
if i replace the disk, with raid 5 can i rebuild and recover the files ?
it happened for no reason.

Thanks a lot

Best regards