> A few years ago I tried to use a RAID1 mdadm array of a SATA > and a USB disk, which lead to strange error messages and data > corruption.
That's common, quite a few reports of similar issues in previous entries in this mailing list and for many other filesystems. > I did some searching back then and found out that using > hot-pluggable devices with mdadm is a paved road to data > corruption. That's an amazing jump of logic. > Reading through that old bug again I see that it was > autoclosed due to old age but still hasn't been addressed: > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/320638 I suspect that it is very easy to misinterpret what the reported issue is. However it is an interesting corner case what could happen with any type of hardware device, not just hot-pluggable, and one that I will try to remember even if unlikely to occur in practice. I was only aware (dimly) of something quite similar in the case of different logical sector sizes. > I would like to ask whether btrfs may also be prone to data > corruption issues in this scenario Btrfs like (nearly) all UNIX/Linux filesystems does not run on top of "devices", but on top of "files" of type "block device". If the block device abstraction layer and lower layers work correctly, Btrfs does not have problems of that sort when adding new devices; conversely if the block device layer and lower layers do not work correctly, no mainline Linux filesystem I know can cope with that. Note: "work correctly" does not mean "work error-free". > (due to the same underlying issue as the one described in the > bug above for mdadm), or is btrfs unaffected by the underlying > issue "Socratic method" questions: * What do you think is the underlying issue in that bug report? (hint: something to do with host adapters or device bridges) * Why do you think that bug report is in any way related to your issues with "a RAID1 mdadm array of a SATA and a USB disk"? > and is safe to use with a mix of regular and hot-pluggable > devices as well? In my experience Btrfs works very well with a set of block devices abstracting over on both regular and hot-pluggable device, as far as that goes. I personally don't like relying on Btrfs multi-device volumes, but that has nothing to do with your concerns, but with basic Btrfs multi-device handling design choices. If you have concerns about the reliability of specific storage and system configurations you should become or find a system integration and qualification engineer who understand the many subletities of storage devices and device-system interconnects and who would run extensive tests on it; storage and system commissioning is often far from trivial even in seemingly simple cases, due in part to the enormous complexity of interfaces, even when they have few bugs, and test made with one combination often do not have the same results even on apparently similar combinations. I suspect that you should have asked a completely different set of questions (XY problem), but the above are I think good answers to the questions that you have actually asked. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
