ZFS

[J65nko]

Dear ZFS guru's

I never had a I386 computer with enough RAM to play with ZFS. I now have one with 2GB memory. Is http://wiki.freebsd.org/ZFSTuningGuide still applicable for such a system?

I only have a single disk in it, but I just want to play with ZFS snapshots and jails.
Any suggestions or helpful advice for a ZFS noob ?

[graudeejs]

Hello, zfs noob (j/k)
This is your lucky day. I have i386 with 2.5GB, and before I replaced one ram module, it had 2GB

vfs.zfs.arc_max=134217728    # 128 MB
vm.kmem_size=536870912        # 512 MB
vm.kmem_size_max=536870912    # 512 MB
vfs.zfs.vdev.cache.size=8388608    # 8 MB

I use these settings in /boot/loader.conf with GENERIC

I also had custom kernel with

options        KVA_PAGES=384

and

vfs.zfs.arc_max=629145600    # 600 MB
vm.kmem_size=1153433600        # 1100 MB
vm.kmem_size_max=1153433600    # 1100 MB
vfs.zfs.vdev.cache.size=8388608    # 8 MB

But you might need to tune these numbers (make them lower). That includes KVA_PAGES. remember that KVA_PAGES must divide by 4 (KVA_PAGES % 4 = 0)


I recommend you start with first pair of settings and GENERIC and see if it will crash or not. I think it will not (also I recommend 8-STABLE or 9)

[vermaden]

Originally Posted by J65nko

Dear ZFS guru's

I never had a I386 computer with enough RAM to play with ZFS. I now have one with 2GB memory. Is http://wiki.freebsd.org/ZFSTuningGuide still applicable for such a system?

I only have a single disk in it, but I just want to play with ZFS snapshots and jails.
Any suggestions or helpful advice for a ZFS noob ?

I currently run ZFS on 1GB RAM box (amd64 through), it uses 2TB ZFS mirror (90%+ full), used for SAMBA and NFS, also for other services, works like a charm without any tuning:

# uptime
11:24AM  up 148 days,  2:26, 2 users, load averages: 0.04, 0.18, 0.11

So 2GB RAM is more then enough, I run 8.2-STABLE amd64 from about 2011-04.

... any reasons to stick to i386?

[drhowarddrfine]

Originally Posted by vermaden

... any reasons to stick to i386?

Cause he's a cheap bastard.

[J65nko]

Vermaden, so the following from http://wiki.freebsd.org/ZFSTuningGuide#amd64 nowadays even seems to apply to amd64 systems with only 1 GB of memory .....

amd64

FreeBSD 7.2+ has improved kernel memory allocation strategy and no tuning may be necessary on systems with more than 2 GB of RAM.

Since several years I have an am64 system with 1 GB of RAM, it is my main desktop system running OpenBSD adm64. Never knew I could have used ZFS on it

The recently acquired 2GB system has a Pentium IV cpu, so strictly i386 only :

OpenBSD 5.0-current (GENERIC) #71: Fri Oct  7 12:57:13 MDT 2011
    deraadt@i386.openbsd.org:/usr/src/sys/arch/i386/compile/GENERIC
cpu0: Intel(R) Pentium(R) 4 CPU 3.20GHz ("GenuineIntel" 686-class) 3.20 GHz
cpu0: FPU,V86,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,
      CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,SBF,SSE3,MWAIT,DS-CPL,CNXT-ID,xTPR
real mem  = 2146693120 (2047MB)
avail mem = 2101518336 (2004MB)
mainbus0 at root
bios0 at mainbus0: AT/286+ BIOS, date 03/17/05, BIOS32 rev. 0 @ 0xf0010,
                   SMBIOS rev. 2.3 @ 0xf04b0 (65 entries)
bios0: vendor American Megatrends Inc. version "1009.001" date 03/17/2005
bios0: ASUSTeK Computer Inc. P5P800

It was previously owned by my wife. My daughter assembled a new quad-core for her mam, so in one way you could call me a lucky, cheap bastard

@graudeejs

Thanks for the tweaks I will try them and report back.

[graudeejs]

BTW: KVA_PAGES value mentioned above was highest I could run FreeBSD without core dumping at boot time. You will need to lower this value (if you'll use it)

[phoenix]

Depending on the P4 chip, you may be able to run the amd64 version of FreeBSD. You'd have to look at it under FreeBSD, though, to see if it supports LM (note the AMD features below, taken from my FreeBSD 8.2 box):

CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2999.92-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf65  Family = f  Model = 6  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=0xe59d<SSE3,DTES64,MON,DS_CPL,EST,TM2,CNXT-ID,CX16,xTPR,PDCM>
  AMD Features=0x20100000<NX,LM>
  AMD Features2=0x1<LAHF>
  TSC: P-state invariant

While you shouldn't need to tune anything, you can guarantee better performance if you do some manually ZFS tunings. Depending on what else you will be running on the box, you will want to limit how much RAM is used by the ZFS ARC. For example, my home "server" runs Samba, NFS, DLNA services, torrent downloading, etc, so I limit the ARC to only 768 MB (out of 2 GB) to leave room for the other services.

You will also want to make sure you disabled prefetching (it should be disabled automatically, but it's good to manually disable it as well).