Eric Sandeen wrote: > Timothy Shimmin wrote: > >> Also from memory, I believe Neil checked this removal into the SLES10sp1 tree >> and some sgi boxes started having slow downs >> (looking at Dave's email below - we were not wanting to tell them >> to use nobarrier but needed it to work by default - I forget now). > > But that's an admin issue. > > The way it is now, for example a home user of md raid1 (me!) can't run > barriers even if they wanted to. > I understand what you are saying. I agree. And I agreed when it went out last time. But as it has: -> gone in <- gone out -> gone in I want to make sure that everyone is happy for it to go back out again. (Cut the string of the yoyo :-) > Until there is a way to know if a write cache is non-volatile the only > safe option is to enable barriers when possible. > >> 6. >>> Date: Wed, 25 Jun 2008 08:57:24 +1000 >>> From: Dave Chinner <david@xxxxxxxxxxxxx> >>> To: Eric Sandeen <sandeen@xxxxxxxxxxx> >>> Cc: LinuxRaid <linux-raid@xxxxxxxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx> >>> Subject: Re: md raid1 passes barriers, but xfs doesn't use them? >>> >>> Yeah, the problem was that last time this check was removed was >>> that a bunch of existing hardware had barriers enabled on them when >>> not necessary (e.g. had NVRAM) and they went 5x slower on MD raid1 >>> devices. Having to change the root drive config on a wide install >>> base was considered much more of support pain than leaving the >>> check there. I guess that was more of a distro upgrade issue than >>> a mainline problem, but that's the history. Hence I think we >>> should probably do whatever everyone else is doing here.... >>> >>> Cheers, >>> >>> Dave. >> So I guess my question is whether there are cases where we are >> going to be in trouble again. >> Jeremy, do you see some problems? > > FWIW, the problem *I* foresee is that some people are going to slow down > when using the defaults, yes, because barriers will start working again. > But I don't see any other safe way around it. > > Education would be in order, I suppose. :) > Well that's an ongoing problem. (Tell 'em to use laptop drives ;-)) --Tim -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
