I'm also running amdump every weeknight, with a single tape, with runtapes set to 2, and considering raising it to 3.
I have autoflush set to on, and I am using a patch so that the maximum flushed plus dumps stays below runtapes * length. The last step isn't completely necessary, but it limits the total amount dumped when things get behind. Each night I perform a tape's worth of dumps, which are written to the holding disk. In the meantime, last night's dump gets written to dump. Sometimes, one night's dump runs over the limit, and is added to the next night's dump. Sometimes, one night's dump is a bit short, and the next night's dump gets added to the flush. Here are the advantages: When there are leftover dumps, the tape drive is busier from the start of amdump until the tape is full. There is no waiting for a dump before a write is possible. In my case, writing the entire tape takes about 12 hours. The tape drive usually available for restores before I leave for the day. With runtapes set to 1, a complete amdump, including the write, often takes more than 20 hours, leaving little time for restores, increasing the risk of not swapping in the correct tape. Inaccuracy of estimates doesn't matter as much. When starting new DLEs, the estimates are often way off. The dumped files are usually not written until the following day. By that time, the true size of the file is known. With runtapes set to 1, when a large file is finally dumped, it is usually the only one available for taping. The tape is usually mostly full at this point. It is common for the large file to be too large for the remainder of the tape, leaving perhaps 30% of the tape unused. With runtapes set to 2, the large files are written at the beginning of the flush, where there is room for them, with smaller files filling out the end of the tape, as it should be. If the estimate for the large dump is too small, this extra room can be filled up with the current days dumps. There will be many files to choose from by the time yesterday taping is finished. Using exclude for samba is not as painful. The estimate may be far larger than the real size, but the backup is often saved until the next day, and the extra space can be used with the current day's dumps. With runtapes set to 1, the extra space goes unused, backing up a small amount of the balanced DLEs if accurate information were known. The most recent backups can be restored quickly. Most of the most recent backup is on disk, so the restore of the most recent backup is quick. Holidays are easier to handle. The backup goes to disk, and moves to tape on the next day when I swap tapes. This methods handles undependable machines better. With my setup, it is common for a machine to go offline for a few days, perhaps skipping level 0 backups. When the machine comes back online, a lot of DLEs get done at once. Disadvantages The primary disadvantage is the need for a holding disk which can handle roughly twice the size of the tape, though I can get away with slightly less space than this. -- Kevin Dalley [EMAIL PROTECTED]