What to do after:" No sd-ext found. Skipping backup of sd-ext"?

I want to update to cyanogenMod 9. But before doing this, I've done a nandroid backup. After the backup was created I saw this output: ClockwordMod Recovery v2.5.1.8 SD Card space free: 1296MB Backing up system... Backing up data... Backing up .android_secure Backing up cache No sd-ext found. Skipping backup of sd-ext. Generating md5 sum... Backup complete! I'm not sure, but I believe this means that the external sd-card partition wasn't backuped. Will this be a real problem, if I want to backup my phone? And how shall I solve it, if it's a problem?