On Wednesday, February 7, 2024 10:50:07 PM CET Wols Lists wrote: > On 07/02/2024 11:07, J. Roeleveld wrote: > >> Because snapshotting uses so much less space? > >> > >> So much so that, for normal usage, I probably have no need to delete any > >> snapshots, for YEARS? > > > > My comment was based on using rsync to copy from the source to the backup > > filesystem. > > Well, that's EXACTLY what I'm doing too. NO DIFFERENCE. Actually, there > is a minor difference - because I'm using lvm, I'm also using rsync's > "overwrite in place" switch. In other words, it compares source and > destination *in*place*, and if any block has changed, it overwrites the > change, rather than creating a complete new copy.
I must have missed that in the man-page last time I used rsync. Will have to recheck and update my notes just in case I need to use rsync again in the future. > Because lvm is COW, that means I have two copies of the file, in two > different snapshots, but inasmuch as the files are identical, there's > only one copy of the identical bits. > > >> Okay, space is not an expensive commodity, and you don't want too many > >> snapshots, simply because digging through all those snapshots would be a > >> nightmare, but personally I wouldn't use a crude rsync simply because I > >> prefer to be frugal in my use of resources. > > > > What is "too many"? > > I currently have about 1800 snapshots on my server. Do have a tool that > > ensures it doesn't get out of hand and will remove several over time. > > "Too many" is whatever you define it to be. I'm likely to hang on to my > /home snapshots for yonks. My / snapshots, on the other hand, I delete > anything more than a couple of months old. > > If I can store several years of /home snapshots without running out of > space, why shouldn't I? The problem, if I *am* running out of space, I'm > going to have to delete a *lot* of snapshots to make much difference... One of the things I didn't like about LVM was that it would have trouble dealing with a lot (100+, due to a bug in my script at the time) of snapshots. And having to manually (or using a script) increase the size given to these snapshots when a lot of changes are occuring. ZFS doesn't have this "max amount of changes", but will happily fill up the entire pool keeping all versions available. But it was easier to add zpool monitoring for this on ZFS then it was to add snapshot monitoring to LVM. I wonder, how do you deal with snapshots getting "full" on your system? -- Joost
