How to reproduce Disk Extender feature of Windows Home Server on linux system
I assume the you know what is Disk Extender about but for those who don't know and who could help here is a short description, what it does, and what I'm looking for.
Disk Extender is a "new technology" introduced by Microsoft on his Windows Home Server operating system.
To make a long story short this technology allow an user to merge several disk into one single disk space (like a raid JBOD or a like a LV with several PV with LVM) but it offer also the possibility for some directory (selected by the user) to be dupplicated to prevent data loss in case of disk failure (like mirroring in RAID 1).
They can do this with 2 or more disk, the space allocated for mirrored data and "normal data" change dynamicaly, following the need of the user.
With LVM I'm able to make one big Logical volume there is no problem.
I could also make redondancy on another LV with RAID 1 but:
When I want a folder to be mirrored I have to copy the full folder from one volume to the other. It could take a while, on WHS is done in a second.
Then the space allocated to redondancy must be allocated dynamicaly and this become very difficult to do.
Finally when you have 3 or 4 disks it become a real mess to handle.
I did not find a way to do it smoothly and this is the question. How to do it ?
Another way to do it could have been to use one sigle LV regrouping all PV and then to use rsync to dupplicate the folder for which I want redondancy but how can I do to be sure that the original and the copy are not on the same disk ?
LVM as no RAID 1 feature as far as I know...
Thanks for your help