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Forum Discussion
ReadyNAS snapshots
Can anyone please clarify how the snapshots are structured in ReadyNas OS?
I see that when I create a snapshot is there in front view.
If I have checked the box to "access the snapshot" (for a share), then two new folders show up at the root level of the share. "snapshot" and ".snapshots". .snapshots is totally hidden from ls listing even in ssh, but if I cd to it anyway knowing is there, I can cd into it.
It appears to me that .snapshots is meant to be the internal location of hard links to underlying snapshot references, they are numbered 0-9 so far. Then the other snapshot folder that is not hidden is also referencing the same things...but labeled as dates rather then sequential numbers.
First I want to understand if I'm understanding that correctly so far?
I am trying to setup my idrive backup to ignore those because to idrive, due to hard links, they just look like lots and lots of duplicated data...twice...once for snapshot and once for .snapshots.
Still trying to figure out out how to exclude them in Idrive, idrive has an exclusion list, but somehow so far its not excluding them..and it takes a really long time to prep its backup task...I guess scanning through many many more data then necessary. I will probably figure that out eventually, but for now just wanting to understand how the snapshots in Readynas work...in terms of those folders when I have enabled "access" to the snapshots.
I wish Readynas had located these access at a different path inside of at the root level of the share, because while readynas is presumably smart enough to ignore that when creating each new snapshot, avoiding recursion.. other tools such as idrive and others, simply see it as a lot of duplicated data.
well anyway it is whatever it is, but any clarity on this point would be helpful. thanks.
5 Replies
So when I unchecked the "Allow Snapshot Access" checkbox, it does remove the /snapshot dir, but the hidden dir called "/.snapshots" is still there, root owned at the root of the share.
Yes, I just double-checked. /.snapshots is there. Don't try to delete this (or the snapshots inside). They are not ordinary folders, they are BTRFS subvolumes (and these are the actual snapshots, not a hard link). Here's what you see with the btrfs commands:
root@NAS:/data/Test/.snapshots# btrfs subvolume show /data/Test Test Name: Test UUID: c4d3f37b-3325-6a47-a333-1ca00266f839 Parent UUID: - Received UUID: - Creation time: 2016-11-09 10:56:50 -0500 Subvolume ID: 296 Generation: 1493758 Gen at creation: 240 Parent ID: 5 Top level ID: 5 Flags: - Snapshot(s): Test/.snapshots/124/snapshot Test/.snapshots/125/snapshot Test/.snapshots/126/snapshotI am not sure what that windows previous version checkbox is for
With Windows 10 and 11, you can right-click on a file or folder and see "Restore Previous Versions". If you enable that option, and then select that option from a PC you'll see something like this:
So this is another way to access the snapshots. It doesn't need access to the web ui, so it is something ordinary users can use. It is also a useful way to see the modification dates of the file (or folder).
Note this is only available on Windows, and you won't see the previous versions if you navigated into the folder from the main volume. For example, if I navigated to \\nas\documents and right-click on a file, I'll see the previous versions. But if I instead navigate to \\nas\data\documents and right-click on the same file, Windows will say there are no previous versions.
Actually once I get local backups happening I am going to turn off snapshots on my main raid anyway and just use it on the local backup
You might instead leave the snapshots on, but use a short retention period. That sometimes will let you recover a file that you inadvertantly deleted before it was backed up.
Yea thanks, I understand what snapshots generally are and how they work. I'm asking about the hidden directory called "/.snapshots" and another non-hidden directory called "/snapshot" that appears at the root level of my share. Please read my previous post again..no need to retype it all out now..
Yea thanks, I understand what snapshots generally are and how they work. I'm asking about the hidden directory called "/.snapshots" and another non-hidden directory called "/snapshot" that appears at the root level of my share. Please read my previous post again..no need to retype it all out now..
I suspect the prior response was AI generated.
If you set "Allow Windows Access" in the snapshot settings, you will see a lot of duplicated data. Also, that setting will change the permissions on the snapshot to Read/Write. That destroys the value of the snapshots for me, since it is far to easy to delete or modify the snapshot. You won't see those folders if you disable "Allow Windows Access". I do keep "Allow Access to Windows Previous Versions" set.
While we're on the subject of Settings... I do NOT recommend using the "Smart Snapshots" setting - instead I use custom snapshots with limited retention, and also set "only take snapshots with changes" The "smart snapshots" retain the monthly snapshots forever - which will eventually fill up the volume unless you periodically delete the oldest ones.
I don't know of any way to set up up the snapshots themselves to present just the changes. But you can use "btrfs send" to copy just the changes to a different folder. Keep in mind that the delta between the main share and each snapshot will increase over time, and more files will end up only in the snapshot when that happens. So if you wanted to automate a daily incremental backup, you'd need to create the snapshot at midnight, and use "btrfs send" to copy the incremental changes in that snapshot the following midnight to a different share. Then create a new snapshot the following day.
Thanks for that.
So when I unchecked the "Allow Snapshot Access" checkbox, it does remove the /snapshot dir, but the hidden dir called "/.snapshots" is still there, root owned at the root of the share.
It's like there are two parallel sets of hard links for the snapshots...one under /snapshot that is enabled by that checkbox in settings, and other that is always there. its extremely hidden, even using "ls -a" does not show it, but you can still cd into it and wala, there are are more hardlinks there.
So first question is, if I turn off "Allow Snapshot Access" is it safe to completely remove that '/.snapshots/" folder or is that that actual way that btrfs is creating the snapshots and they should never be removed? I am uncertain if that folder is related to snapshots entirely or related to the allow access feature.
Unfortunately idrive can still detect that super hidden .snapshots folder and unless I specifically be careful to exclude it, can end up filling up my idrive cloud quota very quickly...that's how I even found out about it.
I did not realize that using "Allow Snapshot Access" changed them to RW, for me that is enough reason to just turn that off period, and if I need to access a versioned file I will just do it through front view. But can I then remove that hidden .snapshots folder or is that fundamentally part of snapshots regardless of access?
I am not sure what that windows previous version checkbox is for, so I will not use it for now, and thanks for the heads up about custom snapshots, I will transition to that. Actually once I get local backups happening I am going to turn off snapshots on my main raid anyway and just use it on the local backup, at which point it would be fine to turn on snapshot access over there, etc..just to make it super simple to navigate to any version I want and get a file from the backup volume.
snapshots on readynas basically act like restore points. they don’t copy all your data, just track changes, so they save space. You can schedule them (hourly, daily, weekly) or take manual ones, and manual snapshots stay until you delete them. If space runs low, the oldest auto snapshots get cleared first. Super handy for quick recovery!
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