NETGEAR is aware of a growing number of phone and online scams. To learn how to stay safe click here.
Forum Discussion
Understanding Migration using ReadyDR to new device and preserve ALL of the current snapshots
Looking to have two NAS units which are syncronized INCLUDING snapshots: I have been happily running my pro6 for many years, backed up a year ago and migrated to 6.6.0 and have continuously upgra...
By experimentation with ReadyDR I am beginning to understand what the behavior is when going from system to system. In particular, ReadyDR looks at the world purely from the perspective of either "shares" or "LUNs", not from the perspective of the entire filesystem. This does make sense, however, it does have some unexpected implications when trying to move to the next machine.
Specifically, if data has been moved between two "shares" and the underlying BTRFS has kept track of the original blocks the original FS may be significantly smaller than the ReadyDR share. Take the following example:
Two Shares, both initially empty (ShareA and ShareB) and a single file, FileA
Copy FileA into ShareA then take a snapshot of both ShareA and ShareB
Move FileA into ShareB and take a snapshot of both ShareA and ShareB
Move FileA back into ShareA and take a snapshot of both ShareA and ShareB
Move FileA into ShareB and take a snapshot of both ShareA and ShareB
Move FileA back into ShareA and take a snapshot of both ShareA and ShareB
Magically, the total consumed disk space is basically just the size of FileA (the wonder of BTRFS)
However, perform a ReadyDR backup of ShareA and ShareB:
The ShareA will have four copies of FileA (in different snapshots) and the total space is four times FileA
The ShareB will have three copies of FileA (in different snapshots) and the total space is three times FileA
This is all exactly what one would expect the FS to do in this case, it just means that the size of a ReadyDR backup can become quite large if there is a significant amount of moving data between shares.
I did find some experimental methods of copying an entire filesystem to new disks which might not have the same underlying structure but not knowing what the ReadyNAS is doing under the hood suggests that there might be unfortunate side effects.
If it were not for desiring to move to Raid6 I would probably just move all of the disks from one box to the other, upgrade them and then rebuild the original.
I am considering a strategy where I use ReadyDR to capture the entire share to the new machine, then clone the most recent snapshot for local use. (these machines are physically seperated and not on the internet). When I bring them together for backup I could run the ReadyDR on each share that is primarily on one box or the other. (i.e. each share has a "primary home" which is the master, it might be on either machine). After the ReadyDR jobs have completed (such that there are full backups all around) then use rsync between the cloned version and the master to incorporate any changes made in the clone, then run ReadyDR again.
The last step would be to depracate the prior clone (either delete or rename) and create a new clone from the ReadyDR archive.
For the most part, the "clones" won't get changes made to them so the frequency necessary is low.
Still working through the best way, did connect the machine to the internet to play with the other features for a bit then will reset to factory again and start working in earnest.
ReadyDR behavior is exactly as expected, some of the shares are becomming quite large and there is obviously duplicates of data between the ReadyDR jobs for each individual share. For the time being "space is cheap" and so will go forward with this plan.
Currently running ReadyDR to specifically named folders on the remote NAS:
MyMusicNAS1 (on NAS1) is sent to MyMusicNAS1ReadyDR (On NAS2)
MyMusicNAS2 (On NAS2) is sent to MyMusicNAS2ReadyDR (On NAS1)
etc
There are many shares on NAS1 which don't need a counterpart on NAS2 because I would not modify the data on NAS2.
I would plan on the "MyMusicNAS2" is not the larger overall archive but rather specific versions, temporary bits, or music collected at NAS2, these are kept in a seperate share and incorporated into "MyMusicNAS1" manually.
Definitely more manual work than I had planned but safe and keeps the manual work of syncronizing data to a reasonable level. Many of these folders are largely static. If doing wholesale rearrangement it is important to do that on the original NAS.
The primary downside is being that NAS1 has 6 drives of 3TB each and all of the data would fit on a single 10TB drive (with a mirror) there is not a way to preserve the snapshot history (where it is connected in revision history) in a clone of a ReadyDR share (i.e. while the ReadyDR share has all of the snapshots included, the clone of the last snapshot in the ReadyDR share does not result in the clone having direct access to the prior snapshots.
Definitely an interesting problem (discussed on various online forums with regard to the BTRFS file system) when there are people in a larger corporation using the revision history to find things. If the primary machine fails and you recover with ReadyDR the recovered "Disaster Recovery" filesystem (i.e. a clone of the last snapshot) does not have ANY of the prior snapshots associated with it. Those snapshots ARE in the ReadyDR share and so it is possible to clone them one by one into individual shares, and it is possible if you start from the earliest and work forward that all would be linked into the same blocks inside the ReadyDR share (so the size does not expand by the number of snapshots), but the ability to walk back through the revision history is lost.
Please don't take this as a critism of the ReadyDR or BTRFS, I am just documenting the implications of how the system works because there are not many people who actually try to impliment their Disaster Recovery plan as they build up the system and want others to understand the limitations.
I am continuing to look at the ReadyNAS external enclosure and wondering if it is a seperate volume can I export it and use that to update the ReadyDR partitions on both machines. i.e. use the "export filesystem" feature for a secondary volume (i.e. /data2 rather than /data) import it into the other ReadyNAS (Yes, I know the Pro6 does not support the external enclosure) run the ReadyDR job and then move that enclosure (or drives) back to the other ReadyNAS.
NETGEAR Academy
Boost your skills with the Netgear Academy - Get trained, certified and stay ahead with the latest Netgear technology!
Join Us!
