On 17.04.19 14:16, Hannes Reinecke wrote: > On 4/17/19 1:32 PM, Manuel Bentele wrote: >> Hi, >> >> On 17.04.19 03:35, Ming Lei wrote: >>> Hi, >>> >>> On Wed, Apr 17, 2019 at 5:33 AM Manuel Bentele >>> <manuel-bentele@xxxxxx> wrote: >>>> Hi everyone >>>> >>>> I'm going to implement an in-kernel reading of QCOW2 images. >>>> In the project, I only need the reading of QCOW2 images, but it's >>>> essential to make thoughts for the implementation of the writing, too. >>>> One of the difficulties seems to be the support of making an image >>>> sparse (resizing the disk image). >>> Could you describe this requirement in a bit more detail? Especially >>> why >>> do you want to read/write QCOW2 in kernel? >> >> Yes, of course. The implementation of reading a QCOW2 disk image >> in-kernel is required for an already existing system in the university >> environment. >> At the moment, the Linux kernel, initramfs, etc. for each client in the >> system is loaded via PXE boot and then the block device with the default >> file system is included with the help of a modified nbd version, called >> dnbd (distributed nbd). >> Due to the fact that the data on the default file system is only for non >> persistent one-time provision of a client, read access is sufficient. >> The user related data is stored on a network storage, as mostly done in >> large scale infrastructures. >> >> Now, the goal is to minimize the network usage and avoid nbd. >> Furthermore, fixed configured and packed boot images should be avoided. >> Therefore, the advantage of the sparse and compression functionality of >> QCOW2 should be used. >> A workaround for that problem could be the local usage of nbd to include >> the QCOW2 disk image as block device, but it involves a lot of >> interaction between user and kernel space and thus an decreasing >> performance. That leads to the motivation to implement the reading of >> QCOW2 disk images directly in the kernel and aim for an merge into the >> mainline kernel source to avoid out-of-kernel-tree maintenance. >> >> If you have any questions related to the described use case or if you >> require more information, please let me know. >> Thanks for your help. >> > cramfs? > Or btrfs with compression enabled? > > Cheers, > > Hannes Thanks for your simple idea to choose cramfs or btrfs with compression enabled. I will suggest that as alternative at the next project meeting. Regards, Manuel
