Rich Freeman posted on Fri, 26 Sep 2014 10:18:37 -0400 as excerpted: > On Thu, Sep 25, 2014 at 5:21 PM, Holger Hoffstätte > <holger.hoffstae...@googlemail.com> wrote: >> That's why I mentioned adding a second device - that will immediately >> allow cleanup with headroom. An additional 8GB tmpfs volume can works >> wonders. >> >> > If you add a single 8GB tmpfs to a RAID1 btrfs array, is it safe to > assume that you'll still always have a redundant copy of everything on a > disk somewhere during the recovery? Would only a single tmpfs volume > actually help in this case? I get a bit nervous about doing a cleanup > that involves moving metadata to tmpfs of all places, since some kind of > deadlock/etc could result in unrecoverable data loss. > > Doing the same thing with an actual hard drive would concern me less.
That has been my concern too, and why I'd be leery about using a loopback on tmpfs, even for the few minutes (more like seconds since I'm on SSD and we /are/ talking memory-backed tmpfs) it'd take to free a minimal number of chunks (say usage=2% or 5% or whatever, the smallest number that actually frees anything). With SSD and with backups I'd probably do it, but it's not something I could recommend, and I'm not sure I'd do it on slower spinning rust, just because the time is longer. I'd probably use a thumb drive or the like, instead, and would certainly recommend that to others, altho if they're comfortable with it and want to risk it, a loopback file on tmpfs should work fine, provided the power doesn't go out in the middle or something. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- 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
