New Transmission add-on thread

My transmission gives of a error message when i start it, and when i restart the NAS it doesn't start. I've so far chucked it up to my NAS running a array in degraded mode, and not thought more of it. Got 6 torrents on it, all on private trackers (3 different) the largest torrent contains 538.65GB in 1948 files. Do you restart the NAS and it turns Transmission inactive, or it just happens "mid flight" so to speak?

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It happens "mid flight". Will try with another torrent now, from a public tracker, just to test.

Connection FailedCould not connect to the server. You may need to reload the page to reconnect.

Thats whats just happening

You could try to reduce the amount of resources that Transmission uses by changing these parameters in the settings.json file:

    "cache-size-mb": 32,
    "peer-limit-global": 50,
    "peer-limit-per-torrent": 10,

Lower values for these settings mean lower resources needed. You can try out a couple of values to see what is working for you. Higher values gives faster transfer, untill your NAS can't handle them anymore. (the peer-limit values can also be set from the webGUI)

Well, JarnoG, numbers are always interesting. I did a bit of fast maths. My NAS is a NV, upgraded with a 1GB RAM stick. Seeing as my global peers limit is set to 75, and torrent peer limit is 50, Anything higher then 13.6 would eat up all my RAM, just for the cache it self, should i ever hit the global peer limit.

With the limit set to 8 i use just about 600MB for cache alone, and speed with 6 completed torrents uploading hits the 2MB/s mark. With the cache set to 16, i hit 1.2MB/s, or there abouts.
It should be noted that performance drops, a fair bit, with the increased cache, even as i'm nowhere near the peer limits, i'm hoowering around the 15 peers mark...
For yet another unknown, setting the cache to a "odd" size, in this case 6MB, made the speeds completely out of whack. It keep bouncing, 300-700KB/s with ocational "highs" just shy of 1MB/s. Not quite sure what would cause this.

Setting cache to a higher number, in this case 32MB, which at my current load would be about half the memory alone, isn't resulting in better performance either.
At this point in my testing, speeds came crashing down, so i assume there are no longer any peers fast enough to load up my connection. It was my intention to go back over the cache sizes again to verify all the numbers with a second 10 minute pass each, but that will apparently have to wait. (I'm also down to 10 connected peers rather then 15, so go figure...)

Cache sizes tested, 4, 6, 8 16 & 32MB. With the exception of 6, it seams less is more, here.
Also, adding and removing a torrent for download with each cache size proves the same point over and over. If you as much as think of downloading, upload speeds come crashing down. I wish it wasn't so, but uploads apparently take priority, in a big way.
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I think the cache-size-mb is the total cash for Transmission, not the cache-per-peer as stated here. However, I noticed that my Transmission is usually using all the spare RAM i've got on my Ultra 2 instead of the 256MB i set it to... When I'm downloading from good seeds, I do see a periodic change in download speed of which the period seems to scale with the cache-size I set.

I don't know if i think your right. Even small changes to cache makes significant changes on my end, where as the 200MB default size was really slowing me down when i started out. Also, i would have to say nothing in the text about cache size say if it's on a / torrent / transfer, or global cache. Well, aside from the conclusion one would possibly jump to after seeing that the default size is 2/4 MB.Your statement that your unit keeps using up all your memory could be due to it trying to allocate x amounts of cache, all at 256MB... At that rate you should see a improvement by dropping cache size, to something similar to mine, 8MB or less.

I don't know, but i always have good seeds, well, good enough to provide better speeds with uTorrent then with Transmission... A lot faster PC then NAS tho, so go figure where the limitation is.
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This post by a Transmission developer mentions increasing the cache size if you have fast swarms or if you are downloading a lot of torrent at the same time, indicating it is a total amount.

Again, i think i have to state that i'm not in total agreement with you.Larger cache on a per torrent, or even per peer basis is beneficial in high speed situations simply since the torrent generates loads of writes with smaller cache. With a lot of competing writes, the darn thing gets nothing done, and your wasting time on waiting for the harddrive subsystem.
I'm not saying i know it's not a global cache size, i don't. I just think it's highly unlikely.

Did you try setting your cache to something small, like 4/8MB and check what it did to your memory usage? While not proving anything, it should give a fair indication by how fast it eats up your RAM.
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I've been trying around a bit and the memory usage has me completely stunned... So far I've noticed that the used amount of memory depends on the setting for cache-size-mb, however, I don't see the relation.
I tried to get an idea by connecting to only a few peers with 2 torrents and changing the cache settings. The torrents each had 200+ seeds and I waited about 5 minutes after starting Transmission. These were the results:
cache-size-mb -> mem used @ peers connected -> avg download speed
2MB -> 10MB @ 14 peers -> ~150kB/s
4MB -> 15MB @ 30 peers -> ~300kB/s
8MB -> 21MB @ 23 peers -> ~400kB/s
16MB -> 33MB @ 15 peers -> ~400kB/s
32MB -> 58MB @ 21 peers -> ~200kB/s
64MB -> 78MB @ 23 peers -> ~150kB/s
128MB -> 44MB @ 25 peers -> ~100kB/s
256MB -> 59MB @ 23 peers -> ~130kB/s

So this obviously wasn't leading to anything useful. Maybe if I would let the torrents download for a few hours that it would stabalize to something useful, but I didn't have the time for that.

After that I tried one torrent (deleting the others) which had about 100 seeds of which I knew that it was very fast. The total size was 175MB. cache-size-mb was 256MB
Downloading at avg 2.5MB/s from 22 peers, Transmission's memory usage peaked at 536MB...
At cache-size-mb of 2MB, that same torrent reached the same maximum speed (~3MB/s) at 24 peers, but the used memory didn't get above 12MB. The download speed did vary a lot though and the average went down to about 1.7MB/s.

Conclusion:
- I've got no idea how it works

Untill someone tells me otherwise, I'll just put the setting back to 256MB. The low free memory doesn't cause any problems as far as I've noticed so I'll just don't look at it ;)

I don't have any means to check memory usage, i'm sure there is a way, i just don't know it, but your test seam to show it's not a global cache at least.
I'm going to guess your test was to short to let the cache find it's full size, but thats just a guess. Thanks for testing.

On the topic of free memory. Just ignore it. 1-7% free is normal on a Linux system. 0% is no good, since it may cause swapping. Other then that, just ignore the free memory figures.
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