Date: Thu, 17 Sep 2009 16:35:37 +0200 From: Anselm Strauss <amsibamsi@gmail.com> To: Steve Bertrand <steve@ibctech.ca>, freebsd-questions@freebsd.org Subject: Re: ZFS on small systems Message-ID: <29722c130909170735w24886ac9j8c5faaed15d17bb9@mail.gmail.com> In-Reply-To: <4AB22B09.4070507@ibctech.ca> References: <7E2DB08A-9E11-47D7-904D-9F3D8490868E@gmail.com> <4AB22B09.4070507@ibctech.ca>
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Thanks for your advice, Steve. I looked a bit at the source code and in /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c and I found this: /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ arc_c_min = MAX(arc_c / 4, 64<<18); Could this mean that 16 MB are already enough to run ZFS? On Thu, Sep 17, 2009 at 2:26 PM, Steve Bertrand <steve@ibctech.ca> wrote: > Anselm Strauss wrote: >> Hi, >> >> I'm interested in using ZFS on one of my small systems with 256 MB of >> RAM and 4 GB flash disk. Since ZFS is now considered production ready on >> FreeBSD I would like to use it as root filesystem and profit mainly from >> the cool snapshot features for easy backups. >> >> I found multiple recommendations to run ZFS only on systems with enough >> resources. But is this only a requirement if you want good performance >> or also for ZFS to function properly at all? > > I've found that on the i386 arch, that at minimum you need 756M of > memory to do anything really useful. Now, I don't know if this has > changed or not, but I doubt that the box would be useful for anything > with only 256M. > > With that said, I can keep a box running at max disk r/w for hours on > end with 2GB, and 1536M allocated/reserved for ZFS. > > Perhaps however that there have been enhancements introduced that I > don't know about, that allow ZFS to operate in such a small memory > address space, but for some reason I doubt it. If I'm wrong, someone > will let us know ;) > > Steve >
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