Date: Wed, 23 Dec 2015 09:07:56 -0800 From: Freddie Cash <fjwcash@gmail.com> To: Stephen Hocking <stephen.hocking@gmail.com> Cc: "hackers@freebsd.org" <hackers@freebsd.org> Subject: Re: The minimum amount of memory needed to use ZFS. Message-ID: <CAOjFWZ4FPo17Z3PiZ97z=%2B-pD4d8ZvLZTFPqnoQ8CofWoWo6PA@mail.gmail.com> In-Reply-To: <CA%2BxzKjDQ_vUfgz4LvvcBE950=-ww7ukCbFmZz1vnzhGrNCucbQ@mail.gmail.com> References: <CA%2BxzKjDQ_vUfgz4LvvcBE950=-ww7ukCbFmZz1vnzhGrNCucbQ@mail.gmail.com>
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On Wed, Dec 23, 2015 at 2:43 AM, Stephen Hocking <stephen.hocking@gmail.com= > wrote: > Inspired by this article: > > http://arstechnica.com/information-technology/2015/12/rsync-net-zfs-repli= cation-to-the-cloud-is-finally-here-and-its-fast/ > > I am wondering about changing my offsite back strategy, which currently i= s > made up of a Raspberry Pi with an external 3TB drive sitting at my > brother's house, with periodic manual rsyncs. I'd like to change that to > doing zfs replications. > > I want to use some of my ARM based hardware as the target for the ZFS > replication, owing to its low power usage. I have a few Cubiboxes floatin= g > around with around 2G of RAM, and a RPI2 or a Banana Pi with 1G. It'd hav= e > a UFS root on the SD card, and ZFS on the external drive. > > Any ideas? > =E2=80=8BMy lowest powered / lowest performing ZFS-based system was an Inte= l Pentium4 3.0 GHz single-core setup with 2 GB of RAM, running 32-bit FreeBSD. Used a 2 GB USB stick for the / filesystem (including /usr), and 4x 120 GB IDE drives in a raidz1. Back in the late FreeBSD 7 / early FreeBSD 8 days. It took a lot of tinkering with =E2=80=8B =E2=80=8Bthe kernel config, loader.conf, and sysctl.conf to make it stable.= But it eventually worked quite nicely. Used it for several years. Even migrated it over to 4x=E2=80=8B 160 GB SATA1 drives in raidz1, then to 500 GB SATA2 = drives in two mirror vdevs, then to ZFS-on-root. The last migration changed the motherboard for one that supports an AMD Phenom-II quad-core at 2.something GHz with 8 GB of RAM. And the to 4x 1 TB drives. Over the holidays, I'll be adding another mirror vdev (total of 3, using 6 drives) and another 8 GB of RAM. ZFS runs better with more RAM; and it requires less manual tuning with more RAM. But it's definitely possible to run it with less RAM. You just need to be willing to spend time tuning, tweaking, and testing. I wouldn't want to run it on an RPi, though. The CPU is just too weak to compute the checksums (unless you go for a weak/fast algorithm) and to do any compression. I've heard good things from people using Intel Atom CPUs, though. --=20 Freddie Cash fjwcash@gmail.com
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