ZFS Recordsize tuning & transmission (bittorent daemon)

[Arnaud Houdelette]

On 19/05/2010 10:46, Matthias Gamsjager wrote:
>> ZFS recordsize on both pools are default (128k). But as transmission
>> bittorrent client has no write (nor read) cache, it could mean that data is
>> written is smaller chunks during download. Could this lead to data being
>> stored in many not-full records ? Does those unfull records would have to be
>> read as whole (128k) during the move, which would explain the above
>> difference on read/write ?
>>
>> I'm just making assumptions here, as my understanding of internals of ZFS is
>> limited. Some insights would be appreciated.
>>
>>      
> Well ZFS does not write immediately but waits couple of seconds and
> write them in 1 single write operation.
>    

That I understand. But bittorrent writes are really random... I'm unsure 
that ZFS is able to aggregates the writes.

> could you give more info about what freebsd version do you use,
> hardware used, zfs parameters in /boot/loader.conf and zfs info like
> compression etc...
>    

uname -a
FreeBSD carenath.tzim.net 8.0-STABLE FreeBSD 8.0-STABLE #0: Tue May 11 
18:29:26 CEST 2010     
tzim at carenath.tzim.net:/usr/obj/usr/src/sys/CARENATH  amd64

Hardware :
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: AMD Athlon(tm) 64 Processor 3200+ (1995.24-MHz K8-class CPU)
   Origin = "AuthenticAMD"  Id = 0x40ff2  Family = f  Model = 4f  
Stepping = 2
   
Features=0x78bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2>
   Features2=0x2001<SSE3,CX16>
   AMD Features=0xea500800<SYSCALL,NX,MMX+,FFXSR,RDTSCP,LM,3DNow!+,3DNow!>
   AMD Features2=0x1d<LAHF,SVM,ExtAPIC,CR8>
real memory  = 1610612736 (1536 MB)
avail memory = 1508560896 (1438 MB)


  - For unsafe:
atapci0: <ATI IXP600 UDMA33 controller> port 
0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0xff00-0xff0f at device 20.1 on pci0
ad0: 152627MB <SAMSUNG HM160HC LQ100-10> at ata0-master UDMA33

  - For tank
ahci0: <ATI IXP600 AHCI SATA controller> port 
0xb000-0xb007,0xa000-0xa003,0x9000-0x9007,0x8000-0x8003,0x7000-0x700f 
mem 0xfe7ff800-0xfe7ffbff irq 22 at device 18.0 on pci0
ada0: <SAMSUNG HD753LJ 1AA01110> ATA-7 SATA 2.x device
ada1: <SAMSUNG HD753LJ 1AA01110> ATA-7 SATA 2.x device
ada2: <SAMSUNG HD753LJ 1AA01110> ATA-7 SATA 2.x device
ada3: <SAMSUNG HD753LJ 1AA01110> ATA-7 SATA 2.x device

zfs get all unsafe/dl
NAME       PROPERTY              VALUE                  SOURCE
unsafe/dl  type                  filesystem             -
unsafe/dl  creation              Thu Nov 26 10:25 2009  -
unsafe/dl  used                  26.2G                  -
unsafe/dl  available             106G                   -
unsafe/dl  referenced            12.6G                  -
unsafe/dl  compressratio         1.00x                  -
unsafe/dl  mounted               yes                    -
unsafe/dl  quota                 none                   default
unsafe/dl  reservation           1G                     local
unsafe/dl  recordsize            128K                   default
unsafe/dl  mountpoint            /store/dl              local
unsafe/dl  sharenfs              off                    default
unsafe/dl  checksum              on                     default
unsafe/dl  compression           off                    default
unsafe/dl  atime                 off                    local
unsafe/dl  devices               on                     default
unsafe/dl  exec                  on                     default
unsafe/dl  setuid                on                     default
unsafe/dl  readonly              off                    default
unsafe/dl  jailed                off                    default
unsafe/dl  snapdir               hidden                 default
unsafe/dl  aclmode               groupmask              default
unsafe/dl  aclinherit            restricted             default
unsafe/dl  canmount              on                     default
unsafe/dl  shareiscsi            off                    default
unsafe/dl  xattr                 off                    temporary
unsafe/dl  copies                1                      default
unsafe/dl  version               3                      -
unsafe/dl  utf8only              off                    -
unsafe/dl  normalization         none                   -
unsafe/dl  casesensitivity       sensitive              -
unsafe/dl  vscan                 off                    default
unsafe/dl  nbmand                off                    default
unsafe/dl  sharesmb              off                    default
unsafe/dl  refquota              none                   default
unsafe/dl  refreservation        none                   default
unsafe/dl  primarycache          all                    default
unsafe/dl  secondarycache        all                    default
unsafe/dl  usedbysnapshots       13.6G                  -
unsafe/dl  usedbydataset         12.6G                  -
unsafe/dl  usedbychildren        0                      -
unsafe/dl  usedbyrefreservation  0                      -

cat /boot/loader.conf
ahci_load="YES"
zfs_load="YES"
vfs.root.mountfrom="zfs:unsafe/root"
#vm.kmem_size="512M"
vm.kmem_size_max="512M"
vfs.zfs.arc_max="150M"
vfs.zfs.arc_min="64M"
vfs.zfs.vdev.cache.size="10M"
vfs.zfs.prefetch_disable="0"

Bad performance IS expected on this hardware. This is a home NAS, and 
the "unsafe" pool is on a laptop 2.5" IDE drive.
Still, bad performance would'nt explain the discrepancies between read 
and write stats (both in zpool io stat and gstat).

> did you test your pool with Iozone to see if it performance as it should?
>
>    

I did not. I just installed the port. What test should I run to get 
relevant data ?


Thanks.