On Tue, May 21, 2013 at 02:22:34AM +0000, Duncan wrote: > zwu.kernel posted on Mon, 20 May 2013 23:11:22 +0800 as excerpted: > > > The patchset is trying to introduce hot relocation support > > for BTRFS. In hybrid storage environment, when the data in rotating disk > > get hot, it can be relocated to nonrotating disk by BTRFS hot relocation > > support automatically; also, if nonrotating disk ratio exceed its upper > > threshold, the data which get cold can be looked up and relocated to > > rotating disk to make more space in nonrotating disk at first, and then > > the data which get hot will be relocated to nonrotating disk > > automatically. > > One advantage of a filesystem implementation, as opposed to bcache or > dmcache, is arguably a corner-case, but it's /my/ corner-case, so... > > I run an intr*-less (I guess technically, empty initramfs) monolithic- > kernel boot, using the kernel commandline root= and (formerly) md= and > related logic to choose/assemble/mount root directly from the kernel > command line via bootloader (grub2). Thus, any user-space-required-to- > mount-root is out, since I don't have an initr* and thus no early > userspace. That means both lvm2 and dmcache (AFAIK) are out. I'm not > sure about bcache, but it has other negatives, particularly against btrfs- > raid-1 and I'd guess md/raid-1 as well. > > Much like md before it, btrfs, while normally requiring the user-space- > required device-scan to properly handle multiple devices, has kernel- > command-line options that allow direct kernel multi-device assembly > without the help of early-userspace/initr*.
I wouldn't be averse to adding such functionality to bcache, provided it could be done reasonably cleanly/sensibly. It's not high on my list but I'd accept patches :) -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html