This error is non-destructive to your data.  It causes speeds to suffer as some of the downloaded chunks get dropped.

File Chunk Memory read and write errors happen occationally because of the way rTorrent is designed.  These errors happen when rTorrent can't load enough chunks into the memory for each connected seed/peer.   It will usually go away eventually.  Unlike Transmission,  rTorrent loads one chunk into the memory for each seed/peer that is active.  Thus, the error happens more with larger chunk sizes and/or greater numbers of simultaneously connected seeds/peers.
 

You will get faster speeds when you avoid this error.

We have taken time to setup standard rTorrent seed/peer settings that avoid the error for most trackers.  We recommend not changing these settings, but depending on the chunk sizes in your torrents and how many torrents are actively seeding/leeching simultaneously, you may need or want to adjust these settings either to avoid the error or increase performance with less common chunk sizes and active seed/peer numbers.

 

Individually for a given torrent, you can control the numbers of seeds/peers rTorrent can connect to by right-clicking on that torrent and choosing 'Properties..'.




 

The Defaults for per-torrent settings can be set in ruTorrent's 'settings' dialog box under 'Downloads' -> 'Bandwidth Settings'.


 

You can also control the total number of upload and download slots in 'Connection' -> 'Other limitations'