On 3/15/2018 6:34 AM, BlackIce wrote:
However the main app that will be
running is more or less a single threated app which takes advantage when
run under several instances, ie: parallelism, so I thought, since I'm at it
I may give solr a few instances as well
Solr is a fully threaded app, capable of doing LOTS of things at the
same time, without multiple instances.
Thnx for the Heap pointer.. I've read, from some Professor.. that Solr
actually is more efficient with a very small Heap and to have everything
mapped to virtual memory... Which brings me to the next question.. is the
Virtual memory mapping done by the OS or Solar? Does the Virtual memory
reside on the OS HDD? Or on the Solr HDD?.. and if the Virtual memory
mapping is done on the OS HDD, wouldn't it be beneficial to run the OS off
a SSD?
There appears to be some confusion here.
The virtual memory doesn't reside on ANY hard drive, unless you've
REALLY configured the system badly and the system starts using swap
space. If the system starts using swap, performance is going to be
terrible, no matter how fast the disk where swap resides is.
The "mapping to virtual memory" feature is something the operating
system does. Lucene/Solr utilizes MMAP code in Java, which then turns
around and uses MMAP functionality provided by the OS.
At that point, that file can be accessed by the application as if it
were a very large block of memory. Mapping the file doesn't immediately
use any memory at all. The OS manages the access to the file. If the
part of the file that is being accessed has not been accessed before,
then the OS will read the data off the disk, place it into the OS disk
cache, and provide it to whatever requested it. If it has been accessed
before and is still in the disk cache, then it won't read the disk, it
will just provide the data from the cache. Getting most data from cache
is *required* for good Solr performance.
http://blog.thetaphi.de/2012/07/use-lucenes-mmapdirectory-on-64bit.html
Running with your indexes on SSD might indeed help performance, and
regardless of anything that's going on, WILL help performance in the
short term, when you first turn the machine on. But if it also helps
with long-term query performance, then chances are that the machine
doesn't have enough memory.When Solr servers are sized correctly,
running on SSD is typically not going to make a big difference, unless
the machine does a lot more indexing than querying.
For now.. my FEELING is to run one Solr instance on this particular
machine.. by the time the RAM is outgrown add another machine and so
forth...
Any plans you have for a growth strategy with multiple Solr instances
are extremely likely to still be possible with only one instance, with
very little change.
Thanks,
Shawn
