ZFS ZFS tweaking on weak systems

Dear Community,
at some point of time when FreeBSD10.3 was up to date I have tried zfs on root using a mirror of
two SSDs and I have been happy with that. The machine I have is not really a performance monster. The first lines of dmesg show
Code:
Copyright (c) 1992-2017 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 11.1-STABLE #2 r324701: Tue Oct 17 21:29:08 CEST 2017
    chris@esprimo.local:/usr/obj/usr/src/sys/ESPRIMO amd64
FreeBSD clang version 5.0.0 (tags/RELEASE_500/final 312559) (based on LLVM 5.0.0svn)
VT(vga): resolution 640x480
CPU: Intel(R) Pentium(R) D CPU 3.40GHz (3391.60-MHz K8-class CPU)
  Origin="GenuineIntel"  Id=0xf65  Family=0xf  Model=0x6  Stepping=5
  Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0xe49d<SSE3,DTES64,MON,DS_CPL,EST,CNXT-ID,CX16,xTPR,PDCM>
  AMD Features=0x20100800<SYSCALL,NX,LM>
  AMD Features2=0x1<LAHF>
  TSC: P-state invariant
real memory  = 2147483648 (2048 MB)
avail memory = 2041008128 (1946 MB)
Event timer "LAPIC" quality 100
ACPI APIC Table: <PTLTD          APIC  >
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
FreeBSD/SMP: 1 package(s) x 2 core(s)
After upgrading to FreeBSD11 I have observed spontanious crashes. In the release notes of FreeBSD11 I read that ARC compression has been enabled by default. Disabling ARC compression in /boot/loader.conf fixed that issue.

Since I run the new kernel the crashes occured again. My RAM is 2GB only but i have seen that the ARC usage has exceeded 1GB. Half of the RAM should be the limit for such a small machine. Limiting the ARC in /boot/loader.conf to 1GB fixed the problem again. Currently ports-mgmt/poudriere is busy building my ports using two builders while I can use a browser to edit this post. No issue so far anymore.

What do you think? Should I re-enable ARC compression on such a machine? Is the need of ARC usage limitation a regression or "just me" issue? Basically I am happy with the overall performance. It is a good opertunity to thank all contributors for the availability of such a nice system :beer::)! Marking the thread prefix with ZFS and Solved seems not to be available ;). The ZFS behaviour shouId be no real problem, as least for me. I just like to know your opinions. Thank you in advance!
 
I think it's worth enabling the compression again just to see if the crashes restart. I would call it a bug if that feature is causing crashes even with ARC limited.

I've always had crashes without limiting ARC though (bearing in mind pretty much all my machines are <8GB RAM). I set ARC such that there's a decent amount reserved for the system pretty much as a matter of course these days.
 
Dear usdmatt,
thank you for the advise. Unfortunately I will be abroad a few days to try that.
Kind regards,
Christoph
 
I think it's worth enabling the compression again just to see if the crashes restart. I would call it a bug if that feature is causing crashes even with ARC limited.
The system is stable with compression enabled and ARC limited to 1GB which is half of the RAM. Thank you for the kind help!
 
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