On 11/01/2017 01:07 PM, Qu Wenruo wrote: > > > On 2017年11月01日 19:31, ST wrote: >> On Wed, 2017-11-01 at 19:17 +0800, Qu Wenruo wrote: >>> >>> On 2017年11月01日 19:04, ST wrote: >>>> Hello, >>>> >>>> I read in different places that one should keep amount of snapshots low >>>> - around 15-20. My question - is this limitation on total number of >>>> snapshots on the system or only on related (parent<->child) chain of >>>> snapshots? >>> >>> Independent subvolume doesn't count, and it's filesystem based. >>> >>> So only snapshots (with source exists, and still shares a lot of trees >>> with source) counts. >>> >>> And if you have multiple btrfs fses, then the count should be based on >>> each fs. >>> >>>> What I want to do is the following: create (and then rotate) last 7 >>>> daily snapshots (and maybe 4 weekly) for each user in his /home dir. >>>> For >>>> around 100 users. So if limitation is only on related snapshots then I'm >>>> OK since only each 7 (or maybe 7+4) of them are related which is well >>>> under the 15-20 limit. However in total there could be 700 snapshots. So >>>> what is true? >>> >>> You're OK since independent subvolumes won't cause too much stress for >>> backref walk. >>> >>> The only thing you may need to consider is to limit the ability to >>> reflink data between subvolumes. >>> Like cp --reflink or even offline dedupe. >> >> Thank you very much! How can I limit this ability? (I'm on Debian9) >> >> All the best! > > No way to limit, unfortunately.
Well, it can obviously be "limited" by just not using cp --reflink all over the place and by not running dedupe on everything. The filesystem won't just start doing that by its own. ;] -- Hans van Kranenburg -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
