Just use the sdcard for /boot and mount rootfs entirely on the hd. Not only will it give you much more storage, but it will also almost eliminate the sdcard failure.

See steptoe's post.

I have 3 Pis, all mounting rootfs on real HDs (one over NFS, and two local), and apart from kernel upgrades, there are no writes to the sdcard (well, except when I play with cmdline.txt and config.txt - but that's just me)