Data Domain: File system panic and reboot when replacing cache tier SSD

• The Data Domain may reboot after cache tier SSD replacement due to a DDFS panic.
• The file system may panic with the message 'PANIC: ddr/lib/dd_flashcache_sl.c: dd_fc_ssd_read_async_cb_handle_entry: 1671'.
• The file system may panic with the message 'PANIC: ddr/lib/dd_flashcache_sl.c: dd_fc_ssd_read_async_cb_handle_entry: 1670'.

Some of the indexed cache entries are not readable after the SSD replacement. The DDFS expected these entries to be readable before the SSD replacement. Since the cached entries are no longer readable, this may trigger a DDFS panic and DD reboot.

1. Disable the DDFS.
2. Replace the cache‑tier SSD and readd it to the system according to the standard cache‑tier SSD replacement procedure for your model DD. Search the Dell Support Site for the model hardware or field replacement guide. 
3. Re‑enable the DDFS after the procedure is complete.