SJS wrote: > begin quoting James G. Sack (jim) as of Mon, Dec 10, 2007 at 04:26:06PM > -0800: >> Tracy R Reed wrote: >>> James G. Sack (jim) wrote: >>>> Whether that's right or not, it's still convenient to call the resulting >>>> capabilities LVM. Now, it strikes me that the unique contribution by LVM >>>> is snapshot and data migration (pvmove). That is, could not the >>>> re-allocation stuff be done outside of LVM? Though I suppose, perhaps >>>> not as dynamically, eh? > > Are those two contributions really unique?
Don't really know. They are not even quite "unrelated to each other", I suppose. Where else do we see snapshot or this kind of migration? Vmware? XEN? something similar in other OSes? >.. >>> Oddly enough I have never really made use of those features. I have >>> played with them of course but 99% of my LVM use is increasing the size >>> of volumes. This is because I usually don't allocate all of my disk >>> space. I usually only allocate what I need and then leave the rest to >>> expand into later. This is much easier than shrinking volumes and then >>> expanding. > > This strikes me as a surperb solution for a single-disk machine. > > Especially with today's monster disks. > >>>> Am I talking any sense, here? Is removing indirection/complication worth >>>> the pain? >>> What do you expect to gain by it? >> Perhaps I should have used virtualization instead of indirection, and >> it's all handwaving, of course, but I was thinking that removing a layer >> could improve performance, mainly latency, I suppose. And not less >> important, I was thinking that there might be simplification leading to >> better maintainability and fewer places for bugs to hide. > > Aren't you talking about ZFS now? ;-) Maybe? I know I've seen gripes about them short-circuiting the "layering". It's sometimes useful to reinvent the wheel, no? >From wikipedia: """ Storage pools Unlike traditional file systems, which reside on single devices and thus require a volume manager to use more than one device, ZFS filesystems are built on top of virtual storage pools called zpools. A zpool is constructed of virtual devices (vdevs), which are themselves constructed of block devices: files, hard drive partitions, or entire drives, with the last being the recommended usage.[6] Block devices within a vdev may be configured in different ways, depending on needs and space available: non-redundantly (similar to RAID 0), as a mirror (RAID 1) of two or more devices, as a RAID-Z group of two or more devices, or as a RAID-Z2 group of three or more devices.[7] The storage capacity of all vdevs is available to all of the file system instances in the zpool. A quota can be set to limit the amount of space a file system instance can occupy, and a reservation can be set to guarantee that space will be available to a file system instance. """ Hmmm, maybe that's had a subconscious impact on my question? Regards, ..jim -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
