Re: ZFS vs OSX Time Machine


On 29/04/2011, at 11:43, Artem Belevich wrote:

On Thu, Apr 28, 2011 at 6:08 PM, Jeremy Chadwick
<freebsd@xxxxxxxxxxxxxxxx> wrote:
I will note something, however: your ARC max is set to 3072MB, yet Wired
is around 4143MB. Do you have something running on this box that takes
up a lot of RAM? mysqld, etc..? I'm trying to account for the "extra
gigabyte" in Wired. "top -o res" might help here, but we'd need to see
the process list.

I'm thinking something else on your machine is also taking up Wired,
because your arcstats shows:

kstat.zfs.misc.arcstats.c: 3221225472
kstat.zfs.misc.arcstats.c_min: 402653184
kstat.zfs.misc.arcstats.c_max: 3221225472
kstat.zfs.misc.arcstats.size: 3221162968

Which is about 3072MB (there is always some degree of variance).

The difference is probably due to fragmentation (most of ARC
allocations are served from power-of-2 zones, if I'm not mistaken) + a
lot of wired memory sits in slab allocator caches (FREE column in
vmstat -z). On a system with ARC size of ~16G I regularly see ~22GB
wired. Ona smaller box I get about 7GB wired at around 5.5GB ARC size.

This system also does double duty as a desktop PC so it gets a fair hammering..

It did have 4GB of RAM but that was fairly terrible, 8GB is a lot better though :)

--
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
-- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C






_______________________________________________
freebsd-stable@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-stable
To unsubscribe, send any mail to "freebsd-stable-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • Re: Automatic reboot doesnt reboot
    ... indicator of ZFS ARC exhaustion, and you seem to know of that. ... Is this box running i386 or amd64? ... RAM size had adverse effects, I've taken the setting out to see if that ... machines are tuned for ARC: we only set one single tunable for ARC ...
    (freebsd-stable)
  • Re: Setting "zfs_arc_max" value in FreeBSD 8.
    ... Now, throw in an SSD for L2ARC, more RAM for ARC (and L2ARC ... OpenSolaris on the same hardware. ...
    (freebsd-hackers)
  • Re: Rasberry Pi dishonesty not thought through properly
    ... Raspberry Pi couldn't look more different from an Arc. ... CPU performance with a highly-efficient, ... backed up by 512Mb of high performance RAM. ... RISC OS 5, with licences from Castle and RISC OS Ltd. ...
    (uk.comp.os.linux)
  • Re: Setting "zfs_arc_max" value in FreeBSD 8.
    ... Anyone know if it is adjustable on a system with 1024MB of ram? ... real memory = 1072107520 ... It needs to be a lot less than kmem_max (the arc is allocated from ... the kernel also need kmem, you need to limit the arc size). ...
    (freebsd-hackers)
  • Re: [PATCH] if_sk(4) rx/tx "hangs"
    ... Ahh fair enough.. ... I have a similarly affected device, but I won't be able to test it until ... Monday (no cable connected to the card, but I added a printf for the RAM ... for Genesis Software - http://www.gsoft.com.au ...
    (freebsd-current)