Date: Wed, 22 Jan 2020 20:07:04 -0600 From: Mike Karels <mike@karels.net> To: Ben Woods <woodsb02@gmail.com> Cc: Conrad Meyer <cem@freebsd.org>, freebsd-arch@freebsd.org, Ed Maste <emaste@freebsd.org>, Philip Paeps <philip@freebsd.org> Subject: Minimum memory for ZFS (was Re: svn commit: r356758 - in head/usr.sbin/bsdinstall: . scripts) Message-ID: <202001230207.00N274xO042659@mail.karels.net> In-Reply-To: Your message of Thu, 23 Jan 2020 08:06:59 %2B0800. <CAOc73CDhPsUkt6aJLSua=9OG5gh_z52qRV0GGMtNaX2=n_5WmQ@mail.gmail.com>
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I took the liberty of changing the subject line to make it stand out a bit more. 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/D2= 3224 > > > > > 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. Convent= ional > > 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 th= at > > has materialized yet. I'm not sure how plausible that is without know= ing > > 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 tunin= g > > 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=3D"ZFS is recommended if you have at least 4GB= RAM" > msg_partitioning_ufs_help=3D"UFS is recommended if you have less than 4G= B of > RAM" > There is some disagree about what these 2 recommendations should be. > 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. > As for the ZFS auto-tuning, I see that as being a separate discussion > (which could ultimately change this recommendation, but shouldn't preven= t > us from committing this help text now). Agreed, but the lack of tuning should factor into the current recommendati= on. Mike > Regards, > Ben
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