Date: Wed, 9 Sep 2015 14:50:14 -0400 From: "Karl Vogel" <vogelke@pobox.com> To: freebsd-questions@freebsd.org Subject: Re: Storage question Message-ID: <20150909185013.GA5368@bsd118.area52.afnoapps.usaf.mil> In-Reply-To: <55F0375D.4070608@FreeBSD.org> References: <55EF3D23.5060009@hiwaay.net> <20150908220639.20412cbd@gumby.homeunix.com> <55EF5409.8020007@yahoo.com> <55EFC2DA.3020101@hiwaay.net> <08B351DD-AA48-4F30-B0D6-C500D0877FB3@lafn.org> <55F02DC8.7000706@hiwaay.net> <20150909150626.5c3b99e5.freebsd@edvax.de> <55F031A0.40500@hiwaay.net> <55F0375D.4070608@FreeBSD.org>
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On Wed, Sep 09, 2015 at 02:42:53PM +0100, Matthew Seaman wrote:
> Actually, ZFS's RAM requirements may not be as gargantuan as all that.
> Despite its reputation for gobbling up all that's available and asking
> for more, it doesn't have to be that way. What takes up the space are
> the filesystem caches, and how much you need for those depends
> absolutely on your usage patterns.
I'm on a Solaris-11.1 system so this doesn't strictly apply, but with
a little tweaking ZFS works pretty well with low memory:
Environment: full X-Windows, Apache, dev stuff (compilers, etc.)
Memory: 4Gb PC3-10600
Chipset: AMD 785G
CPU: AMD Athlon(tm) II X2 B28 Processor, 3.4 GHz, 2MB L2 cache
Disk: 500-GB 3.5" Drive 7,200 rpm, 16MB cache, 3.0 GB/s
I have a second drive with a 32MB cache, and the performance improvement
from the additional memory is significant. My boot settings are below;
hope this helps.
[Yes, I'd love more memory. It's a gov't site, I ordered it last Nov,
and I'm sure it'll be here any day now.]
--
Karl Vogel I don't speak for the USAF or my company
Lois, I think people would prefer a knock to "Pants on".
--Clark Kent chastising Lois Lane for her preferred way
of entering a room on "Smallville".
# -------------------------------------------------------------------------
# Prefetch is on by default, disable for workloads with lots of random I/O.
# or if prefetch hits are less than 10%.
set zfs:zfs_prefetch_disable = 1
# Seems to make scrubs faster.
# http://serverfault.com/questions/499739/
set zfs:zfs_no_scrub_prefetch = 1
set zfs:zfs_top_maxinflight = 64
set zfs:metaslab_min_alloc_size = 4096
set zfs:zfs_scan_idle = 10
set zfs:zfs_scrub_delay = 1
# Enable no write throttling? If your drives can't keep up, you
# can end up with a core dump, according to
# http://hardforum.com/showthread.php?t=1742979
## set zfs:zfs_no_write_throttle = 1
## set zfs:zfs_write_limit_override = 1
# http://dan3lmi.blogspot.com/2012/10/solaris-zfs-tuning-cache-flushes.html
# Looks like it's more for storage arrays or JBODs.
## set zfs:zfs_nocacheflush = 1
# https://rageek.wordpress.com/2012/07/09/strickly-limiting-zfs-arc-cache-size/
# Keep ARC size to about 1/4th memory
set zfs:zfs_arc_max = 1048576000
set zfs:zfs_arc_min = 1048576000
# -------------------------------------------------------------------------
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