Re: btrfs autodefrag?

2015-10-19 Thread Erkki Seppala
Hugo Mills writes: >It has to be disabled because if you enable it, there's a race > condition: since you're overwriting existing data (rather than CoWing > it), you can't update the checksums atomically. So, in the interests > of consistency, checksums are disabled. I

Re: btrfs autodefrag?

2015-10-19 Thread Paul Harvey
On 18 October 2015 at 16:46, Duncan <1i5t5.dun...@cox.net> wrote: > Xavier Gnata posted on Sat, 17 Oct 2015 18:36:32 +0200 as excerpted: > >> Hi, >> >> On a desktop equipped with an ssd with one 100GB virtual image used >> frequently, what do you recommend? >> 1) nothing special, it is all fine as

Re: btrfs autodefrag?

2015-10-19 Thread Austin S Hemmelgarn
On 2015-10-19 02:19, Erkki Seppala wrote: Hugo Mills writes: It has to be disabled because if you enable it, there's a race condition: since you're overwriting existing data (rather than CoWing it), you can't update the checksums atomically. So, in the interests of

Re: btrfs autodefrag?

2015-10-19 Thread Erkki Seppala
Austin S Hemmelgarn writes: > And that is exactly the case with how things are now, when something > is marked NOCOW, it has essentially zero guarantee of data consistency > after a crash. Yes. In addition to the zero guarantee of the data validity for the data being

Re: btrfs autodefrag?

2015-10-19 Thread Austin S Hemmelgarn
On 2015-10-19 12:13, Erkki Seppala wrote: Austin S Hemmelgarn writes: And that is exactly the case with how things are now, when something is marked NOCOW, it has essentially zero guarantee of data consistency after a crash. Yes. In addition to the zero guarantee of

Re: btrfs autodefrag?

2015-10-18 Thread Xavier Gnata
On 18/10/2015 07:46, Duncan wrote: Xavier Gnata posted on Sat, 17 Oct 2015 18:36:32 +0200 as excerpted: Hi, On a desktop equipped with an ssd with one 100GB virtual image used frequently, what do you recommend? 1) nothing special, it is all fine as long as you have a recent kernel (which I

Re: btrfs autodefrag?

2015-10-18 Thread Hugo Mills
On Sun, Oct 18, 2015 at 10:24:39AM -0400, Rich Freeman wrote: > On Sat, Oct 17, 2015 at 12:36 PM, Xavier Gnata wrote: > > 2) Disabling copy-on-write for just the VM image directory. > > Unless this has changed, doing this will also disable checksumming. I > don't see any

Re: btrfs autodefrag?

2015-10-18 Thread Rich Freeman
On Sat, Oct 17, 2015 at 12:36 PM, Xavier Gnata wrote: > 2) Disabling copy-on-write for just the VM image directory. Unless this has changed, doing this will also disable checksumming. I don't see any reason why it has to, but it does. So, I avoid using this at all

Re: btrfs autodefrag?

2015-10-17 Thread Duncan
Xavier Gnata posted on Sat, 17 Oct 2015 18:36:32 +0200 as excerpted: > Hi, > > On a desktop equipped with an ssd with one 100GB virtual image used > frequently, what do you recommend? > 1) nothing special, it is all fine as long as you have a recent kernel > (which I do) > 2) Disabling