Date: Fri, 14 Mar 2014 19:36:48 +0100 From: =?iso-8859-2?Q?Edward_Tomasz_Napiera=B3a?= <trasz@FreeBSD.org> To: Ian Lepore <ian@FreeBSD.org> Cc: freebsd-hackers@FreeBSD.org, RW <rwmaillists@googlemail.com> Subject: Re: GSoC proposition: multiplatform UFS2 driver Message-ID: <0405D29C-D74B-4343-82C7-57EA8BEEF370@FreeBSD.org> In-Reply-To: <1394811577.1149.543.camel@revolution.hippie.lan> References: <CAA3ZYrCPJ1AydSS9n4dDBMFjHh5Ug6WDvTzncTtTw4eYrmcywg@mail.gmail.com> <20140314152732.0f6fdb02@gumby.homeunix.com> <1394811577.1149.543.camel@revolution.hippie.lan>
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Wiadomo=B6=E6 napisana przez Ian Lepore w dniu 14 mar 2014, o godz. = 16:39: > On Fri, 2014-03-14 at 15:27 +0000, RW wrote: >> On Thu, 13 Mar 2014 18:22:10 -0800 >> Dieter BSD wrote: >>=20 >>> Julio writes, >>>> That being said, I do not like the idea of using NetBSD's UFS2 >>>> code. It lacks Soft-Updates, which I consider to make FreeBSD UFS2 >>>> second only to ZFS in desirability. >>>=20 >>> FFS has been in production use for decades. ZFS is still wet behind >>> the ears. Older versions of NetBSD have soft updates, and they work >>> fine for me. I believe that NetBSD 6.0 is the first release without >>> soft updates. They claimed that soft updates was "too difficult" to >>> maintain. I find that soft updates are *essential* for data >>> integrity (I don't know *why*, I'm not a FFS guru).=20 >>=20 >> NetBSD didn't simply drop soft-updates, they replaced it with >> journalling, which is the approach used by practically all modern >> filesystems.=20 >>=20 >> A number of people on the questions list have said that they find >> UFS+SU to be considerably less robust than the journalled filesystems >> of other OS's. =20 Let me remind you that some other OS-es had problems such as truncation of files which were _not_ written (XFS), silently corrupting metadata = when there were too many files in a single directory (ext3), and panicing = instead of returning ENOSPC (btrfs). ;-> > What I've seen claimed is that UFS+SUJ is less robust. That's a very > different thing than UFS+SU. Journaling was nailed onto the side of = UFS > +SU as an afterthought, and it shows. Not really - it was developed rather recently, and with filesystems it = usually shows, but it's not "nailed onto the side": it complements SU operation by journalling the few things which SU doesn't really handle and which used to require background fsck. One problem with SU is that it depends on hardware not lying about write completion. Journalling filesystems usually just issue flushes instead.
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