On 06/09/2010 09:08 PM, Daniel Lezcano wrote: > On 06/09/2010 08:45 PM, Gordan Bobic wrote: >> Is there a feature that allows unifying identical files between guests >> via hard-links to save both space and memory (on shared libraries)? >> VServers has a feature for this called hashify, but I haven't been able >> to find such a thing in LXC documentation. Is there such a thing? >> >> Obviously, I could manually do the searching and hard-linking, but this >> is dangerous since without the copy-on-write feature for such >> hard-linked files that VServers provides, it would be dangerous as any >> guest could change a file on all guests. >> >> Is there a way to do this safely with LXC? > > No because it is supported by the system with the btrfs cow / snapshot > file system. > > https://btrfs.wiki.kernel.org > > You can create your btrfs filesystem, mount it somewhere in your fs, > install a distro and then make a snapshot, that will result in a > directory. Assign this directory as the rootfs of your container. For > each container you want to install, create a snapshot of the initial > installation and assign each resulting directory for a container.
OK, this obviously saves the disk space. What about shared libraries memory conservation? Do the shared files in different snapshots have the same inodes? What about re-merging them after they get out of sync? For example, if I yum update, and a new glibc gets onto each of the virtual hosts, they will become unshared and each get different inode numbers which will cause them to no longer be mmap()-ed as one, thus rapidly increasing the memory requirements. Is there a way to merge them back together with the approach you are suggesting? I ask because VServer tools handle this relatively gracefully, and I see it as a frequently occurring usage pattern. Gordan ------------------------------------------------------------------------------ ThinkGeek and WIRED's GeekDad team up for the Ultimate GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the lucky parental unit. See the prize list and enter to win: http://p.sf.net/sfu/thinkgeek-promo _______________________________________________ Lxc-users mailing list Lxc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lxc-users
