I thought it might be worth repeating what Dave Hitz said on this subject last December:

The "snap list" command lists the snapshots in order, and it includes the amount of space locked down by each snapshot individually, and also the cumulative amount locked down by each snapshot along with all younger snapshots.

If two snapshots in a row lock down lots of blocks individually, but the cumulative amount doesn't change, then that means they are locking down the SAME blocks. If the cumulative does change, then that means they are locking down DIFFERENT blocks

For the oldest snapshot, you can tell how much space it'll free up by looking at the cumulative for all snapshots before it, and the cumulative for it. The difference is what will get freed up. (Does this make sense? You won't get the full amount reported for that snapshots individually, because others will be referencing many of the same blocks.)

For intermediate snapshots, you can kind of get a feel for what's going on by looking at the individual and cumulative sizes, once you get the hang of it, but there's no way to tell for sure how much space will be freed up.

It's funny. One of our concerns when we initially designed snapshots was that they would just be too complicated to manage. They really are complex and confusing. Still, we hoped that in normal practice they would work fairly intuitively, since create patterns in a large FS don't tend to change that rapidly, and when you do have a problem you can just crank back the schedule a bit.

For the most part, I think we got lucky, but sometimes when people ask questions like this, I realize how fundamentally complex snapshots really are.

Dave

At 12:13 PM 11/17/98 -0600, you wrote:

On 11/17/98 09:26:50 you wrote:

...

Hi All,

Eventhough my snap list shows less than 100%, Why my df command shows 130%?

Is there any hidden files that I need to delete? How does this sanp list matches with df's capacity?

The percentages in snap list have always been a little confusing. I think they give you the amount of space the snapshot takes up relative to the total disk space used on the filer, and the total disk space available on the filer. Neither of which would relate to the space you've chosen to reserve for snapshots. I could be wrong, though; I don't have a man page handy and frankly, I've always pretty much ignored the values in snap list as they didn't really contain any useful information to me.

All the 130% means is that you've exceeded your snapshot reserve. You have a couple of choices:

1. If you think this is typical and don't mind the space usage, increase your snapshot reserve.
2. If you think this is typical and DO mind the space usage, you will need to change your snapshot schedule to exclude, for example, the weekly snapshots.
3. If you think this is not typical, and you simply had a bunch of stuff deleted this week, you can either live with it for a day or two until it's deleted "naturally", or delete it manually yourself.

There are some other things you could do too, but those are the main options.

Bruce