Can anyone tell me what exactly the VBD extents are used for in the XEN back-end block device driver? It almost looks like each virtual disk is made up of multiple physical drives if I read the code correctly (for each VBD grow message received by blkback, it opens a device and retreives various info such as its size). Thanks, Eric --------------------------------- Do you Yahoo!? Yahoo! Mail - Find what you need with new enhanced search. Learn more.
> Can anyone tell me what exactly the VBD extents are used for > in the XEN back-end block device driver? It almost looks > like each virtual disk is made up of multiple physical drives > if I read the code correctly (for each VBD grow message > received by blkback, it opens a device and retreives various > info such as its size).The extent stuff is left over from Xen 1.2, where we effectively had to do our own version of LVM inside Xen. We''d like to give the code a spring clean and do away with the grow/srink control messages altogether. At the same time it would be sensible to add support for multiple blk rings, and possibly the ability to ''tunnel'' certain ioctls e.g. eject CD. Ian ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It''s fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel
So in XEN 2.0 is VBD grow/shrink used? I searched through the source code and could not find anyone who is generating these messages to blkback. From my understanding, blkback needs the VBD extent info to generate the I/O requests to the real disk device driver (the physical disk on domain 0). If indeed these messages will eventually be removed, i take it XEND will need to send a message to blkback identifying the disk device driver it should use for I/O (by supplying it a device ID like with the VBD extents). Eric Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk> wrote:> Can anyone tell me what exactly the VBD extents are used for > in the XEN back-end block device driver? It almost looks > like each virtual disk is made up of multiple physical drives > if I read the code correctly (for each VBD grow message > received by blkback, it opens a device and retreives various > info such as its size).The extent stuff is left over from Xen 1.2, where we effectively had to do our own version of LVM inside Xen. We''d like to give the code a spring clean and do away with the grow/srink control messages altogether. At the same time it would be sensible to add support for multiple blk rings, and possibly the ability to ''tunnel'' certain ioctls e.g. eject CD. Ian ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It''s fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel --------------------------------- Do you Yahoo!? Yahoo! Mail - 250MB free storage. Do more. Manage less.
> So in XEN 2.0 is VBD grow/shrink used?Yes, Xend uses them when creating a VBD. Xend first creates a given VBD, which starts off with zero size. Xend then adds exactly one segment to the VBD using a grow message - this segment describes the device the VBD is mapping. Shrink messages probably aren''t used anywhere at all.> 0). If indeed these messages will eventually be removed, i take it XEND > will need to send a message to blkback identifying the disk device driverThat sounds right - basically just removing the vestiges of multi-extent support in blkback so that each VBD has exactly one extent. Cheers Mark> Eric > > Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk> wrote: > > Can anyone tell me what exactly the VBD extents are used for > > in the XEN back-end block device driver? It almost looks > > like each virtual disk is made up of multiple physical drives > > if I read the code correctly (for each VBD grow message > > received by blkback, it opens a device and retreives various > > info such as its size). > > The extent stuff is left over from Xen 1.2, where we effectively had to > do our own version of LVM inside Xen. We''d like to give the code a > spring clean and do away with the grow/srink control messages > altogether. At the same time it would be sensible to add support for > multiple blk rings, and possibly the ability to ''tunnel'' certain ioctls > e.g. eject CD. > > Ian > > > ------------------------------------------------------- > The SF.Net email is sponsored by: Beat the post-holiday blues > Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. > It''s fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/xen-devel > > > --------------------------------- > Do you Yahoo!? > Yahoo! Mail - 250MB free storage. Do more. Manage less.------------------------------------------------------- This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting Tool for open source databases. Create drag-&-drop reports. Save time by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc. Download a FREE copy at http://www.intelliview.com/go/osdn_nl _______________________________________________ Xen-devel mailing list Xen-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/xen-devel