zfs, 1 gig of RAM and periodic weekly

Charles Sprickman spork at bway.net
Mon Feb 27 23:40:46 UTC 2012

On Feb 27, 2012, at 5:48 PM, Freddie Cash wrote:

> On Mon, Feb 27, 2012 at 11:02 AM, Nenhum_de_Nos
> <matheus at eternamente.info> wrote:
>> On Mon, February 27, 2012 15:33, Chuck Swiger wrote:
>>> On Feb 26, 2012, at 9:07 PM, Eugene M. Zheganin wrote:
>>> [ ... ]
>>>> all with zfs and one gig of RAM.
>>> This isn't a sensible combination; I wouldn't try to run ZFS on anything less than 4GB...
>> regardless of the pool size ?
>> I was planning on making an atom board a file server for my home, and I have two options: soekris
>> net6501 2GB RAM and intel board powered by the 330 atom (says 2GB limited as well). My plans are
>> to use from 4 up to 8 disks, and they should be 2TB at least.
>> As its for home use, some p2p software and mostly music listening and sometimes movie streaming.
>> should 2GB be that bad, that I should drop it and use UFS instead ?
>> I may run any version of FreeBSD on it, was planning on 9-STABLE or 9.1.
> You can get away with 2 GB of RAM, if you spend a lot of time manually
> tuning things to prevent kmem exhaustion and prevent ZFS ARC from
> starving the rest of the system (especially on the network side of
> things).
> Definitely go with a 64-bit install.  Even with less than 4 GB of RAM,
> you'll benefit from the large kmem size and better auto-tuning.
> Do not, under any circumstances, enable dedupe on a system with less
> than 16 GB of RAM.  :)
> If at all possible, find a motherboard that will let you use more RAM.
> 2 GB is usable.  But 4 GB is the sweet spot for a simple file server.
> And 16 GB is best for a system with over 10 TB of storage in the
> pool.
> My home media server is a 32-bit install of FreeBSD 8-STABLE (Dec 2011
> vintage) with only 2 GB of RAM, using 4x 500 GB SATA drives in 2
> mirror vdevs (boot off USB stick).  Every couple of weeks it'll lock
> up, usually under heavy torrent load.  Prior to doing a bunch of "tune
> loader.conf; reboot; crash; repeat" cycles, the box was very unstable.
> 2 GB is barely enough for ZFS + NFS + Samba + torrents + whatever.

Sounds very familiar.  Substitute afp for samba and torrents for sabnzbd
furiously unpacking things and we're probably doing much the same.  3 1TB
Samsungs (+1 spare), 2 gmirror'd CF cards for boot.

[spork at media ~]$ uptime
 6:41PM  up 60 days,  8:36, 1 user, load averages: 0.00, 0.02, 0.00
[spork at media ~]$ zpool list
tank1  2.72T  1.89T   850G    69%  ONLINE  -
[spork at media ~]$ grep avail /var/run/dmesg.boot 
avail memory = 2087931904 (1991 MB)
[spork at media ~]$ uname -a
FreeBSD media..com 8.2-RELEASE FreeBSD 8.2-RELEASE #1: Tue Feb 22 04:44:55 EST 2011     spork at media..com:/usr/obj/usr/src/sys/MEDIA  i386

Just in case I've hit on some special sauce in the loader.conf,
here you go:

[spork at media ~]$ cat /boot/loader.conf 

I used to be able to panic it regularly, but I just kept stepping the 
kmem up and the arc down until it behaved.  The uptime would be longer
if my power wasn't as flakey.


> -- 
> Freddie Cash
> fjwcash at gmail.com
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