Date: Wed, 22 Jan 2020 19:11:31 -0800 (PST) From: "Rodney W. Grimes" <freebsd-rwg@gndrsh.dnsmgr.net> To: mike@karels.net Cc: Ben Woods <woodsb02@gmail.com>, Philip Paeps <philip@freebsd.org>, freebsd-arch@freebsd.org, Ed Maste <emaste@freebsd.org>, Conrad Meyer <cem@freebsd.org> Subject: Re: Minimum memory for ZFS (was Re: svn commit: r356758 - in head/usr.sbin/bsdinstall: . scripts) Message-ID: <202001230311.00N3BVju027378@gndrsh.dnsmgr.net> In-Reply-To: <202001230207.00N274xO042659@mail.karels.net>
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> I took the liberty of changing the subject line to make it stand out a > bit more. Thanks, good idea, I seem to have missed some of this thread. > Ben wrote: > > > On Sat, 18 Jan 2020 at 09:16, Mike Karels <mike@karels.net> wrote: > > > > > On Fri, 17 Jan 2020 at 08:21, Ben Woods <woodsb02@gmail.com> wrote: > > > > > > > > Perhaps we could simply include a message on that bsdinstall > > > partitioning > > > > > mode selection screen that UFS is recommended on systems with < 4 Gb > > > RAM? > > > > > > > > > > > > I have uploaded a diff for this here: https://reviews.freebsd.org/D23224 > > > > > > > Please let me know your thoughts (comments in the phabricator review > > > would > > > > be best). > > > > > > I think this needs more discussion, preferably on this list. I am not > > > convinced that systems with as little as 4 GB should use ZFS. Conventional > > > wisdom on the FreeNAS mailing list says that 8 GB is required for ZFS, > > > and FreeNAS no longer includes UFS as an option. Conrad suggested a > > > cutoff of 16 GB; I am happier with 16 GB than 4 GB as a cutoff. Also, > > > there was mention of auto-tuning for smaller systems; I don't think that > > > has materialized yet. I'm not sure how plausible that is without knowing > > > the workload. I use ZFS on a workstation/server with 64 GB that runs 4 > > > bhyve guests that do things like buildworld. ZFS wants 63 GB for arc_max; > > > needless to say, I have a tunable set to a much lower value. If tuning > > > is required, it is unclear that ZFS is a good default. > > > > > > Mike > > > > > > > Hi everyone, > > > Before I commit phabricator review D23224, is there any final comments? > > > Particularly on these 2 lines of help-text: > > msg_partitioning_zfs_help="ZFS is recommended if you have at least 4GB RAM" > > msg_partitioning_ufs_help="UFS is recommended if you have less than 4GB of > > RAM" > > > There is some disagree about what these 2 recommendations should be. ZFS is recommended if you have read the ZFS memory tuning guide :-) I have run it in some pretty tiny memory configurations, with proper tunning including 32bit nodes with 512MB of memory and no other memory intense processes. > > 4GB was recommended by: imp, emaste, philip, eugen, dteske > > 8GB was recommended by: mike > > 16GB was recommended by: cem > > > The 4GB limit seems to have the best consensus, however there was some > > debate about whether ZFS is recommended on a system with 4GB, or only > > systems with MORE THAN 4GB. > > I don't remember what everyone else wrote, but IIRC, Devin said that if > you use ZFS with 4 GB, you will soon end up with a dozen tunables set. > That doesn't sound like a recommendation for 4 GB. >From my perspective ZFS is a great thing, BUTT in no case where I have it installed is it running with out of the box settings. In all cases I minimally tweak vfs.zfs.arc_max as the default for this leaves systems with a configuratoin that invariable runs into OOM issues. Until that issue is fixed for me it is a mistake to make ZFS default on any system, no matter how much memory it has. > > > As for the ZFS auto-tuning, I see that as being a separate discussion > > (which could ultimately change this recommendation, but shouldn't prevent > > us from committing this help text now). > > Agreed, but the lack of tuning should factor into the current recommendation. And I agree with Mike here, these tuning issues defanitly should affect our choices of default install recomendations. > Mike > > > Regards, > > Ben -- Rod Grimes rgrimes@freebsd.org
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