How do Openspace servers allocate resources?

I think this something that should be understood by anyone who contemplates buying or renting an Openspace sim. Does anyone know the answer?

If I acquire a quarter of a full sim, I know that anything I do will affect the other 75% -- and conversely, anything that happens elsewhere on the sim may affect my parcel.

If I acquire an Openspace sim, I have the whole sim to myself -- but I share a server with the owners of 3 other Openspaces. To what extent do activities on those sims affect my sim?

I guess that the Openspace servers are set up so that each of the 4 sims is limited to 25% of the available memory and CPU time -- because that is the only sane solution. Otherwise anyone could set up a sex club on an Openspace, and make the other 3 unusable.

But how does it really work?

The reason I am asking is that I am interested in renting an Openspace -- but I have already had disagreeable experiences with both mainland and estate land, and I don't want to make another mistake.

I have asked two estate managers this question, and neither of them knew the answer. Hopefully somebody here does!

If four openspace sims share the resources of one server, then that's exactly what they do.

I've been to a few openspace builds and they always seemed laggy to me. YMMV.

It is 1 regular SIM per "core" not per server, but per "virtual machine" (one per core). So an OpenSpace SIM is shared with other 3 OpenSpace sims on a single core, it means that on a Quad Core (and they are almost all class5 now) there are 16 OpenSpace SIM, so your OpenSpace is shared with other 15 residents OpenSpaces (in random order/placement).

We do not have any documentation about resource allocation per virtual machine, so none know (Linden apart) if there's really a mechanism that allocate (memory and CPU) resources per SIM, i guess there's none because they wanted to optmize the resource usage.. so if someone have just water the other resources would be available for other (more intensive) simulators... but u gonna face the problem you mentioned above: one sim is capable to (potentially) disrupt all other sims running on the same core, if not on the same server.

The optimal solution would be a load balancing between virtual machines, so in example if none of the others are actually using so much resource, the one that needs it would be able to allocate them... *BUT* when someone else requests to use "their" resources, the previous allocation must be regained back. I think a system like this is not currently in place, because talking about Mono they said: "in the future we may have a script resource allocation, because Mono would permitt it... etc.", so i assume there's none actually.

*IF* none of the solutions are above is implemented, it's still anyway strange, because a resource allocation (per applications: since the simulator and the LSL2 enviroment are just running tasks) may be done via OS tools... so assuming they aren't doing it, i don't know the real reason.

Yes, of course. But I would like to know HOW the resources are shared.

Here is an analogy. I have a Virtual Private Server at http://www.linode.com/ . In SL language, I use it to bang things. Each machine hosts several Virtual Private Servers, but the allocation of resources for each VPS is rigorous and scrupulously fair. Although is it theoretically possible for me to bring down the whole machine, I would have to work quite hard to make it happen -- and in practice it does not happen. So everybody is happy, and nobody has to think about the other VPSs.

It's the only sensible way to run a VPS business. Do the Lindens think in the same way?



That is what I want understand -- what is causing the lag ... something on the Openspace you are in, or on one of the others?

So far, all the Openspaces I have visited seem fine to me, with no evident problems. I'm concerned about what *might* happen to an Openspace which I would be paying for. Strange thing about SL -- anything that can happen does happen, doesn't it?

Thanks for your insights Vittorio.

It's what I was hoping *not* to hear!

If the Lindens are not load balancing now, it must be because they do not have a good way to do it.

I have no idea about the load-balancing, but in my experience openspace sims have been very good. I usually get about 60 avies going through my sim in an average day but rarely more than 10 at one time and there are no issues with lag.

If your intention is to use an openspace for a business with a high traffic volume, then no - openspace isn't for you because those sharing the processor will suffer while you hog the resources.

Ok, that implies that resources *can* be hogged. That is my concern -- it is possible for my low-traffic operation to be damaged by a high-traffic business on a different Openspace that I am not even aware of?

It's conjecture based on observation and thus not truly empirical.

But if your low-volume operation is in a mainly residential block you should be ok. Problem is it's impossible to know which sims share which processors - unless somebody knows how to do this - in which case i would defintely like to know.

I think it also depends alot on where you rent your sims - in Otherland, where Nature's Way is the area I occupy is entirely residential* - so traffic is generally low. Buffy's Cove is only really permitted because it is not a commercial business - if I charged people entry I would be violating the terms of the Otherland covenant

*The minimun rent being a quarter sim - although most have halves

The problemi is not the traffic, neither the loading with prims (they are limited anyway), but there's a HUGE difference with scripts performance (including attachments indeed), they runs from 30% to 50% slower than a regular simulator. You should rez any object containing a script where the slow runs is visually noticiable (eg: a puppet... or those pets that changes their primitives placement to make "poses" to figure immediatly how poor the result is on a OpenSpace.
Luckily Mono is almost here, this would be a great improvement for these OpenSpaces SIMS.. i've did test on my SIM fully converted to mono, and the script performances increase floats around from 3 to 6 times faster! That's the main reason i'm impatient for mono releasing on the maingrid.. it's scary because of potential trouble the first day (imho there will be much more troubles than with the H4 introduction), but the benefits upon the "costs" are so big that i would loose weeks to (eventually) fix and recompile my scripts but with the happiness of watching em running at lightspeed.

As far as I have seen, the open sims on the same core will effect eachother because one single openspace sim can preform like a regular sim one minute and lag to death the other without changing anything, it's doubtfull they effect the other 12 openspace sims very much or at least not more then with regular sims.

Luckely there is a selution to the problem of openspace share lag, most openspace owners (myself included) will give renters and subleasers/buyers (watever term you prefer) estate rights so you can restart the sim, this will put it on a different server giving a good change to be lag free again.

*ping*

The penny drops - I get it - sims are not on a fixed server they float around on different servers or more accurately virtual machines depending on when they are restarted. So one day you might be in Texas, another in California.

That means you never actually know which sims you are sharing with because it changes...

OpenSpace sim performance is highly variable depending on a number of factors.

OS sims share one processor with 3 other OS sims, and share all other system resources (memory, local HDs, network interfaces, etc) with 15 others. Thus, if you get a very CPU-intensive process going on in one or more of the other 3, your sim will start lagging, too, as if you were doing some serious crunching in your sim (and if you are, you will affect the other 3). If a memory, HD, and/or network-intensive process is going on with ANY or many of the other 15, then yours will seem to lag, too.

We recently had a new OS sim owner at the Isle (running on a Class 5) who started getting ping times of >1000ms to his sim. He had the Lindens investigate, and it turned out that one of the other 3 he was sharing with had >20 avatars in it at an event. They restarted and moved his sim to another CPU/server host, and the problem went away.

In general, my experiences with OS sims (on both class 4 and 5 hosts) have been mixed, but generally rather dismal. However, I am a scripter, and I note when scripts start taking a long time to do their jobs. Chatloggers that lose >50% of the chat going through them, as an example. In general, script performance seems be the most impacted. Even in the best of conditions, scripts in OS sims take at least twice as long to complete many tasks than in a normal sim.

For what they were intended, flying/walking/boating through an open space (like a low-prim park, open water, etc), they are great. Static builds work just fine. Low population density makes them bearable.

However, I would never own one as my primary home/place of business. I DEFINITELY would not run vendors, servers, etc. Anything business-critical needs to be in a full sim.

Class 5 Servers are not Quad Cores, according to SL blogs this is a "Class 5" server:

So, here’s what’s different under the hood: we’ve been all-AMD for years, but are moving from the Opteron 270 to the Intel Xeon 5148 - a low-power version of Intel’s new Core 2 Duo based server CPUs. This gives us better performance for fewer watts, while supporting our standard 64-bit OS image. We’ve also doubled the RAM per machine from 2GB to 4GB and moved to a faster SATA disk, which usually won’t make much of a difference, but should reduce the stalls sometimes seen by heavy regions during autosaves. Finally, there are fewer, bigger system fans, and power supply efficiency goes from 67% to 84%; power usage while running the sim process is about 175 watts, vs. 230 for a Class 4.

These are actualy pretty old servers now, this post was from mid 2006. Only 4 gigs of ram per server? heck I run 8 gigs on my home computer.... and what apears to be a single SATA hard drive? most servers now run Raid arrays.

The 5148 is a nice cpu, but is one of the older 65 mn chips, replacing them with a 45mn Quad and bumping the Ram up to 16 or so gigs and setting up a raid of a set of 10,000 rpm drives and you would see a noticable improvement.

but of course that would be a pretty major investment for LL to make.

They use blade servers.

Each blade has 2 processor slots, so with a dual-core CPU, that means they are quad-core.

The sim processes don't need much HD except for swap, the OS, the SL software, and scratch area to hold the sim state (which is snapshotted and uploaded to a special inventory server cluster every hour or two, I believe). As such, RAID and 10,000RPM drives would be overkill. Plus, being a blade, they have little room for such.



In 2006, 4 gigs was still a lot of memory, even for a server. Considering most of what the simulator software does, memory size really isn't as much of a factor.



I have a feeling that they are keeping up with technology advances. Server "class" isn't so much an exact specific set of hardware they use until they upgrade, but a general class of hardware which can have incremental upgrades within, like a faster, lower-power processor, more memory, a bigger HD, etc. So, what passed for a Class 5 server in 2006 is probably not exactly the same as what their hardware supplier is delivering to them today.

There's no reason to do in-situ upgrading; it is cost prohibitive. They will just wait until a blade fails, or they sunset it, then replace the entire blade with a newer, faster one of the same Class.

Thanks Talarus. The implications are becoming clearer now ... even normal activity may create problems in Openspaces. Elsewhere, nobody would complain about an event with 20 avatars. But Openspace owners and renters must develop Openspace attitudes, practices and mentality.



That is clear enough. I have no business plans, so I should be OK in an OS.

Thanks for this information Abigail. That is something new I have learnt today. I would not have known to ask about that before renting -- but now I do know.

I suppose conscientious estate managers would be proactive and restart a lagging OS as sson as they noticed it.

Now I am wondering what else I don't know!

Has anyone got a critical checklist for tyro OS renters?

Note that a simple restart will not necessarily move the sim from the current host. The reason it worked for the folks at the Isle is that the Lindens got involved, and did something on the back end to make sure it moved when restarted.

This has been a mixed-bag function in the past. For a long time, manual restarts would move regions to a different host, then it kept you on the same region for a while. Not sure right now which it does, but my point is don't depend on this functionality to be a reliable way to get your OS sim moved from a loaded host to a less loaded one.

I can vouch for the fact the OS sims are slow. I rent half of one on a brand-new 'class 5' and use it for my main store as well as staging my live music shows once or twice a week. I don't run any sophisticated scripts. The most complex script I run is Rez-Faux which runs agonisingly slowly in OS sims.

OS sims suit my epic scale style of building so it works just fine for me. YMMV.

There's been a billion posts on this subject, but I'll summarize:

- Openspaces are light use.
- They can handle Avatars and builds fine, scripts resources are limited.
- From my own experiences you'll start to see your scripts slow at about 600 scripts. (A full region can usually handle well over 5000 before having issues).
- Some types of physical items (fish, dogs, or other animated physical things) can sometimes cause dilation issues.

Other than that, they are pretty good