Can I do revolving backups?

[CharlieN]

I’m considering buying an EX2 to use for home backups, and I have a question about the auto-rebuild functionality of the RAID 1. What I would like to do (assuming I have three drives numbered 1, 2, and 3):

1. Install drives 1 and 2 in RAID 1 configuration and back up my computer.
2. Remove drive 1 and insert drive 3. I believe the RAID will rebuild itself and drive 3 will now be identical to drives 1 and 2.
3. Take drive 1 to offsite storage.
4. After a month of ongoing backups, bring drive 1 back and use it to replace drive 2. My hope is that the existing contents of drive 1 would be wiped and it would be reinitialized as a mirror of drive 3.
5. Take drive 2 to offsite storage.
6. Repeat monthly.

Does anyone know if this works? Really the question is what the system does if you insert a disk which already contains data and was already known to the system in the past.

[ArMak]

Hi there,

I have not tried this, in theory it should be possible, but lets see if another uses has tried to do this and can give you some information regarding this matter.

[george_h]

Tricky… It is rather twisting the purpose of mirroring (RAID 1) to acheive something which is much more easily achieved by simply plugging one of several USB hard drives in, backing up to that (if you can get the backup to work, there appear to be issues), unplugging the USB drive then storing that. The following month you use a different USB hard drive.

Mirroring works best when it can mark one drive as “dead” or “failed”. It then can switch to solely using the other drive and ignoring the “dead” one. Then when you replace the “dead” drive with a different one, it has to recognise (or be told) that it has a working replacement. Once that happens it should then just overwrite everything to make it a mirror of the other (still “working”) drive.

[CharlieN]

Thanks George - I appreciate the input on it. You’re probably right that an external USB drive would be a simpler way to attack the problem.

[george_h]

If you have problems getting the built-in backup to work when backing up from NAS to USB (symptoms like it never finishes or just seems to stall - it says it is still running but there is no disk LED activity for ages), try changing the “Backup Type” setting (in the backup job when you create it) from “Copy” to “Synchronise”. Then make sure you specify a destination folder on the USB drive that doesn’t exist - it will create it.

While for the some the built in backup seems to work fine, for myself on some others it doesn’t and doing the above seems to be a workaround. It allows me to backup 336GB successfully that way.

Currently awaiting an answer from WD Support on that issue.