The Second Life world
consists of many, interconnected, uniquely-named simulators
(also referred to as sims
on a Cartesian map
with its origin at the global coordinates 1000, 1000
sim). A sim's global coordinates can be accessed by calling llGetRegionCorner
and dividing the results by the size of a sim (256m on a side). Neighbouring sims are connected vertically and horizontally, but never diagonally. This grid
forms the world (image
) of SL
. Sims also seem to have an integer
that represents a group
for which the sim shows up on the world map (there are hidden sims; if you are in a hidden sim, all other hidden sims designated to the same group will show up on the world map).
The dimensions of a sim are unvaried: 256m x 256m. Non-physical Objects
instantly move down to 4096 meters if they go above 4097 meters
on the z axis
(height) if they move after going above 768 meters. (physical
objects currently go off-world at 4096m
). Sims always have land
, although it can be completely submerged in water
. Any open space between non-adjacent sims is visibly rendered as water on the client
, but cannot be accessed (the avatar
will bounce off an invisible wall).
There is currently a limit of 15,000 primitives
per sim, and approximately 100 agents
. Though intended to optimize server
and client performance, these numbers are arbitrary and likely to be increased again in the future. (Initially, the limit was 10,000 prims and approximately 20 agents.)
Open-space sims (also known as void sims) have a limit of 3750 primitives
per sim. A agent has to own a standard sim to get Open-space sims.
A sim keeps track of the objects and agents within it, simulates physics
, runs scripts
, and caches
and delivers object and texture
data within the sim to clients, both within ("agents") and looking into the sim ("child agents"). Sims also handle attachments
, which are really just special objects that match an avatar's location
, and don't count against the sim's prim limit.
Simulator names are restricted to 20 characters(counting spaces) which may be split into 3 alphanumeric words.
Each sim is powered by a single PC CPU core, either an , running Debian
Linux, though there may be multiple CPUs, cores, and sims per machine (1100 servers, ~2000 CPUs -2/22/06
) or strona
. There are no more than 4 sims per machine (2 dual-core CPUs per box).
Open-Space Simulators are run on the same servers as the main ones, but they are packed 4 to each CPU core.
Apparently, the sim software uses a pretty sophisticated journaling storage system (database) for objects, allowing a fast (usually) recovery with minimal data loss after a crash, power outage, etc.
"The company [Linden Lab
] also chose to store the avatars that its nearly 60,000 users [10/17/5] have created in a file system front-ended by the open-source Apache
Web server, while the open-source Squid
Web proxy cache keeps the data conveniently nearby. Metadata about the avatars is stored in an open-source MySQL
"Second Life has 240,000 registered users. ... Second Life currently runs on 2,579 servers that use the dual-core Opteron chip produced by AMD. Each server is responsible for an individual "sim," or 16 acres of virtual "Second Life" land. At peak usage that means that each server is handling about three users." -
Outsourcing service Indonesia
| sim names