Hi list. I'd have a few questions about the alignment issues and about how to generally set up dm-crypt. I've read http://www.saout.de/pipermail/dm-crypt/2010-February/000584.html, but it's still not fully clear to me how this alignment thingy works. I have to scenarios: A) Sofware RAID6, multiple partitions each to be encrypted. (Using the kernel md for the software RAID) B) Single SSD disk, multiple partitions each to be encrypted. Regarding A: 1) What is generally the best way to do this? I mean how to stack the different levels of md/RAID, [LVM] (if used at all), dm-crypt. I'd say one has about this: (physical disk[s]) --> (MD/RAID6) --> (dm-crypt) --> ([LVM] if used at all) --> filesystem Or is another order "better"? I think having MD/RAID at the bottom makes sense (instead of dm-crypt at the bottom), at this should make recovery easier, right? I'm not sure whether I need LVM at all, but I think it makes only sense to have it on top of dm-crypt in order to use to use it to enlarge volumes. I guess one cannot enlarge a LUKS "filesystem", even if the an unterlying LVM volume would be enlarged? 2) I guess at any of the levels from above, one can partition the exported block device, right? So e.g. partition the physical disks that each has one big sdX1, and create the RAID on it _OR_ create the RAID directly on the disk withoug partitioning. Is there any prefered schema, especially so that alignment works better on any level? I'd have it done the following way: (physical disk[s]) ---no_partitions---> (MD/RAID6),... directly on the respective /dev/sdaX... not on any partitions --- several partitions (e.g. one for boot, root, home, data and so on) on the RAID device ---> (dm-crypt/LUKS),... one on any partition ---[not using LVM at all]---> filesystems Does this sound reasonable? 3) Now regarding the alignment. I use Debian sid, with 2.6.33. Does this already work out of the box? I guess not. As far as I understood, I must align each level, right? How can I do this on each? When I create the MD/RAID on a non partitioned device. How can I tell mdadm to do the correct alignment. And when I create several partitions on that RAID, will cryptsetup automatically align LUKS? And last but not least. How do I make the filesystem aligned within the LUKS device? Is this dependant from the filesystem type? I'd like to use btrfs and ext4. 4) I guess I have no 4K HDD but would the system automatically get this done right, just in case I have one? Regarding B: 5) Are there any special things I have to consider for the alignment on an SSD or is it the same then above? (I mean alginment is really important for SSD because of the wear...) 6) Milan wrote, that one needs to align to the 4MB boundary... how&why? Thanks in advance. Hope that wasn't too off topic :) Sincerely, Philippe. _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
