| Rich Freeman on 12 Oct 2015 10:27:09 -0700 |
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| Re: [PLUG] Video link: "Virtualizing Bare-Metal Systems with QEMU" and meeting bookmarks |
On Mon, Oct 12, 2015 at 1:17 PM, Keith C. Perry <kperry@daotechnologies.com> wrote: > Yep, that's might I made mention of "raw" disk images. :) > Sure, but I'm just not sure what the connection is to bind mounts. > Since I usually keep the system volume separate for my vm (or at least when I am building them) I can loop mount the partition then do whatever bulk data moves are needed (e.g. move source code for later compiling) and then convert back to qcow2. Makes sense. > > Fun fact... sharing a raw disk image between a VM host and guest does seem to work (I did that a when I was building some FOSScon usb multiboot keys) but I'm not sure its "safe". You would have to take care to make sure you are not making changes to the same files at the same time. YMMV > Yeah, you DEFINITELY do not want to mount a disk image on multiple kernels unless the filesystem is specifically designed to handle this (very few are, and nothing you'd find on a typical linux install). Filesystems designed to handle being mounted by multiple kernels are called clustered filesystems. It isn't sufficient to just avoid changing the same file at the same time - the kernels will be stomping all over each other's metadata and can hose potentially anything on the device. The other approach to multiple mounting is a distributed filesystem. In this arrangement any particular device is only accessed by a single kernel, but the filesystem itself exists at a higher level than any single kernel and uses networking/etc to distribute data across all nodes that access it. The most popular examples of this sort of thing are HDFS and Ceph. This approach tends to be more popular than clustered filesystems, since it does not require giving high-speed access to a single device to all the nodes that need to share it. -- Rich ___________________________________________________________________________ Philadelphia Linux Users Group -- http://www.phillylinux.org Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug