[Soekris] Poor I/O performance

Thomas Fjellstrom thomas at fjellstrom.ca
Wed Mar 12 06:30:15 CET 2014


On Tue 11 Mar 2014 11:32:37 AM Karsten Kruse wrote:
> Ahoi,
> 
> i have a bunch of net6501-70 for evaluation and they show poor I/O
> performance.
> 
> I use CentOS 6.5 with kernel 2.6.32-431.5.1.el6.x86_64 and this is my disk:
> 

Linux firewall 3.12.0-rc3+ #3 SMP Mon Oct 21 17:15:52 MDT 2013 x86_64 GNU/Linux

I get about the same as you. My read speeds are higher, around 130MB/s, but 
testing write speeds to my Crucial m4 gets me 20MB/s. I thought that was more 
or less normal for the mSATA slots. Maybe I'm wrong though. I certainly would 
expect that m4 card to get much higher than 20MB/s write on its own, so it 
likely isn't the card that's slow. Specs say 260MB/s.

> [root at sonde04 ~]# hdparm -i /dev/sda
> 
> /dev/sda:
> 
>  Model=Samsung SSD 840 EVO 120GB, FwRev=EXT0BB0Q, SerialNo=S1D5NSADB40689E
>  Config={ Fixed }
>  RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=0
>  BuffType=unknown, BuffSize=unknown, MaxMultSect=16, MultSect=16
>  CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=234441648
>  IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
>  PIO modes:  pio0 pio1 pio2 pio3 pio4
>  DMA modes:  mdma0 mdma1 mdma2
>  UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
>  AdvancedPM=no WriteCache=enabled
>  Drive conforms to: unknown:  ATA/ATAPI-2,3,4,5,6,7
> 
>  * signifies the current active mode
> 
> 
> Looks good to me, UDMA6 is used. This doesn't look as good:
> 
> 
> [root at sonde04 ~]# time dd if=/dev/sda of=/dev/null bs=1M count=1024
> 1024+0 Datensätze ein
> 1024+0 Datensätze aus
> 1073741824 Bytes (1,1 GB) kopiert, 14,0558 s, 76,4 MB/s
> 
> 
> So this is read, this is what write looks like:
> 
> 
> [root at sonde04 ~]# sync ; time { dd if=/dev/zero of=/tmp/test.dd bs=1M
> count=1024 ; sync ; }
> 1024+0 Datensätze ein
> 1024+0 Datensätze aus
> 1073741824 Bytes (1,1 GB) kopiert, 47,0048 s, 22,8 MB/s
> 
> real    0m50.428s
> user    0m0.022s
> sys     0m7.021s
> 
> 
> This is 1 GB (power of 2) written in 50 seconds, so that amounts to
> about 20,5 MB/s. Would anyone be so kind and run the commands himself,
> maybe with Debian or something with a more recent kernel.
> 
> Also i would appreciate any tips on how to get a bit more write
> performance. We would like to monitor traffic with it, using NtopNG and
> tcpdump. When we dump traffic, we don't write payloads, just headers, so
> we don't need more than maybe 40 MB/s guess.
> 
> 
> Have a nice day,
> 
> Karsten Kruse

-- 
Thomas Fjellstrom
thomas at fjellstrom.ca


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