Tags are stored in your catalog file. If you want to have them available after a disk crash, you need to make regular and automated backups of your catalog file to a different physical disk. You can turn this on in Lightroom via Catalog Settings->General->Backup. Note: you still have to also make backups of your photos, this feature in Lightroom does NOT make backups of your photos.
If at some point in time, you consider moving away from Lightroom, you can also write the tags to the photos themselves (or in the case of RAW, to sidecar XMP files). This can be done by selecting all photos and then Metadata->Save Metadata To Files (note: this will take a long time if you have selected a lot of photos). You can also turn on the option to do this automatically Catalog Settings->Metadata->Automatically write changes to XMP. Any tags written via this method are readable by any other photographic application that I know of.
Thanks. That's positive news. Any down side to putting the data right on the file from the start?
If you are asking is there a downside to the option to do this automatically, my answer is NO