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I'm using a Dell PowerEdge R210 II server with Intel Xeon E3-1230, 32GB RAM DDR3, 2 x 480 GB SSDs SATA3, 2 x 1 Gbit network connection. I'm using both network connections at the same time (802.3ad bond).

The problem is... I get poor IO performance with rTorrent (0.9.4/0.13.4) and Debian 7. At first, the download speed gets above 200 MB/s then, as IO load reaches 100%, it slows down and stabilizes at about 120-130 MB/s.

The SSDs are almost new. I have tested them and they reach ~500 MB/s on both read/write.

Trim is activated, all volumes are formatted as ext4. I'm using deadline as I/O scheduler (judging from my tests, it seemed to be the best in my case).

The network connections work as they should. I have reached constant speeds of ~200 MB/s on FTP transfers.

This is my current /etc/sysctl.conf:

net.ipv4.tcp_reordering=127
net.core.netdev_max_backlog = 30000
net.core.rmem_max = 67108864
net.core.wmem_max = 67108864
net.ipv4.tcp_rmem = 4096 87380 33554432
net.ipv4.tcp_wmem = 4096 65536 33554432
vm.dirty_background_ratio = 40
vm.dirty_ratio = 70
net.ipv4.tcp_congestion_control=htcp
net.ipv4.tcp_mtu_probing=1

These are the limits of the rtorrent process:

Limit                     Soft Limit           Hard Limit           Units
Max cpu time              unlimited            unlimited            seconds
Max file size             unlimited            unlimited            bytes
Max data size             unlimited            unlimited            bytes
Max stack size            8388608              unlimited            bytes
Max core file size        0                    unlimited            bytes
Max resident set          unlimited            unlimited            bytes
Max processes             257642               257642               processes
Max open files            16384                32768                files
Max locked memory         65536                65536                bytes
Max address space         unlimited            unlimited            bytes
Max file locks            unlimited            unlimited            locks
Max pending signals       257642               257642               signals
Max msgqueue size         819200               819200               bytes
Max nice priority         0                    0
Max realtime priority     0                    0
Max realtime timeout      unlimited            unlimited            us

One (possibly important) observation is that if I disable the write caching on both drives (with hdparm) there is a noticeable boost in IO performance.

I use the SSD drives separately (no RAID).

Any suggestions will be much appreciated. Thank you!

RazvanR104
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  • Bittorrent (small chunks, many remote hosts) is quite different in terms of network traffic from FTP (small or large chunks, single remote host). You can't necessarily say that the speed you're getting with one will be the same as that for the other. – user May 14 '15 at 22:27
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    Where is this system hosted. Are you sure you are not be throttled by your ISP? – Zoredache May 14 '15 at 22:33
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    It's hosted in NL. I am sure it's not throttled by my ISP. I'm asking for some optimizations for better I/O with rTorrent and SSDs. – RazvanR104 May 15 '15 at 06:33
  • Have you tried tweaking resource limits in rtorrent config, for instance `network.max_open_files = 100`? See some suggestions at https://whatbox.ca/wiki/rtorrent – Nemo Jul 22 '22 at 08:49

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