OVH 1Gbit Server rtorrent high IO

randac56

Member
May 25, 2018
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I come here for advice.

Here's my situation. I am renting a dedicated OVH server, to be precise this one: http://www.ovh.ie/dedicated_servers/eg_best_of.xml

Specs:

-1Gbit
-24GB RAM
-Intel Xeon W3520 4x2(HT)x2.66+ GHz CPU
-2x 2TB - SATA2 in soft RAID 0

I share this server with two others, so we're with three total on this machine. We're each running 50+ torrents, each person running an instance of rtorrent. OS is Ubuntu, nothing major changed in configuration from default.

The problem we're having is Disk I/O. If we all have our rtorrent clients running with 50+ torrents, the Disk I/O reaches 99.99% making the server unusable slow. If however 1 person runs a single well seeded torrent on the server, it will get 60MB/s download speed, which is of course very good.

So when the Disk I/O goes 100% and unusable for everyone, the CPU is barely running and RAM is only using 2GB out of 24GB.

What I'm basically asking is, is there a way for me to improve the Disk I/O performance on this server?

We have been looking at a bigger server, this one: http://www.ovh.ie/dedicated_servers/mg_best_of.xml but of course we don't want the same issues as we already have... this one does have SSD's as an addition though to the HDD's.

I hope someone could give advice.. thanks!!
 

simur612

Member
May 25, 2018
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Don't expect SSDs to be some sort of magical pixie doest which solves _all_ of the I/O bottlenecks for _writes_.

It's not about how much MB/s youre sending/receiving but most importantly to how much peers youre talking to at a time.

rtorrent is notoriously bad at humongous public swarms where you need to have 700 peers (each at 5kb/s) to get decent download speeds. Try deluge/utorrent if you need that - they optimize this case at the expense of higher CPU/RAM usage.

SSDs are awesome, but freakishly small.

It certainly helps to have that SSD dedicated for new downloads, and move the torrent to sata disk once it's complete.

There are more things you can try:

Use -o writeback ext4. Keeping the default data journalling is always major source of I/O contention on torrents.
Ditch CFQ, use deadline.

If possible, don't use stripe (RAID 0), but dedicate each disk per user (!). Again, you don't need pure MB/s, but IOps.

Btw, 24GB ram is a bit of overkill. It's useful only if you're going to partition that server into openvz/xen instances or have 10 users, each running deluge.