So here is what I do: Declare an array, go through each item of array. The difference is almost 200 times in perf. 6 sec in .net and 10 minutes in PS.  

After discussion with the PS product team. Found out the reason. So since PS is interpreted vs a compiled .net you would expect some perf difference. But internally what PS does is if a loop iterates for more than 16 times, then on the 16th iteration the content of the loop is compiled dynamically as a .net code and the dynamic method is then invoked inside the loop. Great. The only gotcha being that the dynamically invoked method could be a security risk (think viruses duplicating itself) so .net runs a security check on the stack and that is what is slowing the loop down for long running loops in PS.

Workaround:
==================
We can declare .net code inside PS using the Add-type command. And this way the dynamically invoked method will encapsulate the loop and the iteration so the security check is only done once. Running the code below I consistently got performance similar to .net if not better in few cases.

# declare a buffer
$buffersize=1024*4
[Byte[]]$ba = new-object Byte[] $buffersize
$linecount = 1
$ba[30] = 10
$ba[300] = 10
$start = [System.DateTime]::Now

$source = @"
   public class myArrayIterator
   {
                public static int GetCount(byte[]b, byte tofind)
                {
                    int count = 1;
            int lastcount = 0;
                    int max = b.Length ;
            do
            {
               
                {
                    if (b[lastcount] == tofind) { count++; }
               }
                lastcount++;
            } while (lastcount < max);
                   return count ;
                }
   }
"@

Add-Type -TypeDefinition $source

$count = [myArrayIterator]::GetCount($ba, 10)
write-host "Count - " $count

$end = [System.DateTime]::Now
$time = $end - $start
write-host "Time taken -" $time

Hope this helps with your long running loops in Powershell.

Here are my suggestions for my customers for using alternatives to Timer jobs in SP2013.

If you look at the basic need for Timer jobs it usually boils down to either performing scheduled tasks and/or that an event has occurred in a SP data structure (List/doc lib/pages). There are sometimes needs for a sync job where a timer job syncs data between two sources.

1. SP Workflow : SP workflows can be used for doing event based triggers (usually if sending email is involved). Also with Site workflows they can be on long timer delays and can run in a loop to query for data changes and then perform appropriate actions.

2. Events:  List based events can be used to trigger a remote event to manage the data change activity as well.

3. Outside Scheduler : This is the most similar experience to SP timer jobs except there will be no access to server side OM. Outside schedulers either custom .net schedulers(windows service) or Azure scheduling service can be used to trigger code on a time based fashion to perform the operations. Few people I have seen have used "Task Scheduler" in the OS and I personally do not like that option as I am not sure how well it scales.

Now from these three options I am most interested in the 3rd option.

It would be a cool project to write a custom .net service which is installed as an application and is fully trusted to query for data. This service then runs forever and is scanning a predefined list (read from an xml file), you upload your custom dll to this list along with the schedule information on when to run this dll. The service will eventually pick up the dll along with the schedule and call a predefined method (say "Execute") for you in the dll by reflection. Since the service is fully trusted the code should be able to access any list data and can perform various email operation as long as SMTP are properly configured. This will provide for a drop your dll and schedule to run on a schedule and access SP data.
Will let everyone know once I have the code ready for this :). Comments are welcome.

http://www.microsoft.com/microsoftservices/en/us/support_premier_devs.aspx

As soon as I got my feet wet(which basically meant I installed SPS server). Rahul, I am not really sure what I did that irked him off so much that he pushed me into the dark alleys of search, custom Filter and protocol handlers. Comming from the COM world where everything that can be thought of was already documented, the muddy waters of IFilters and protocol handlers were as clear to me as the swamps of florida which I had visited last weekend. So I decided to write my own implementation of IFilter and Protocol Handler. I am done with the Filter part now and would be working on the Protocol Handler comming weeks.I guess the real problem with someone like me who has not dealt much with searching and crawling components is that it's difficult to imagine where and how our component would be fit and who and when would our methods be called. Where here is my take on what I understood of it: Filters based on IFilter for MS Indexing server is what SPS uses to Fitler out contents, this was simple enough.

The whole design of SPS search is divided into two individual parts:
1. CRAWLING: In this phase the server will crawl any content source, i.e. a file share, a .html page etc. By crawling it means that it would try to extract text and properties of that document and index those in a flat file index. So a crawler would call a protocol handler based on what type of content source it is, the protocol handler would know how to open that content source and then call the IFilter implementation for the respective File type to get its properties and text.
2. SEARCHING: Once a content source has been indexed any search can be performed on this index. Isn't this cool.
Jumping straight to Filters. Filters are basically written to customize the content of a particular file type so it can be indexed efficiently. So for eg. if my app's document has a .ant extension and it stores the name of users in a struct. I would need a Filter to open the file, read the structures, get out the name inside the struct and save it in the indexer. That is the real power of IFilters.

Now how do we write one, heh heh, allright for all those code junkies(me included). Here is a good MSDN link for more technical details:http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odc_SP2003_ta/html/ODC_HowToWriteaFilter.asp?frame=true

But basically to summarize Protocol handler would open a content source, get to a file, and based on its extension it would call the Filter that has been registered for that extension to index it. So basically we are interested in these 4 methods in a Filter:
1. Init: This is where you would do initialization for your filter.
2. GetChunk: This method gets called to read the file and get a chunk of text or properties.  
3. GetText:
4. GetValue: Once a chunk has been read, GetValue or GetText would be called based on the chunk type that we set in GetChunk till it returns FILTER_E_NO_MORE_TEXT or FILTER_E_NO_VALUES.

That is it. That is all it requires to write a filter(well not really you would need to have a good understanding of COM, pointers, variant data types and C++ programming). The simplest thing to get started is the simpFilt sample that comes with SDK. To install the filter:
1. Compile it and regsvr32 the dll.
2. In Regedit goto HKLM\software\Microsoft\SPSSearch\ContentIndexCommon\Filters and add the name of the extension your filter will be crawling and in the default value put the CLSID of your dll.
3. From SPS portal site go to Site Settings->Configure Search and Indexing->Include File type   and add the extension for your filter.
4. Now add a content source where the file with the registered extension is stored and do a full crawl and voila your filter is up and running.
Probably the best way to get a deeper look is to Open the filter project in VS.net and attach to the msadmn.exe process and put breakpoints on those 4 methods.
Currently  I  am writing a IFilter for Windows Media files(wmv and wma). It's gonna be pretty cool once its ready. I had some trouble with the Media Format SDK but couple of links from Santosh and I was reading those properties like Arial Font 16. My Filter can crawl the document and get the properties out but the indexer somehow is not indexing them properly. But i hope to sort that out this week.

Wow this log turned out to be pretty long but would post the Media filter as soon as its done.

How to set:
==========
Unfortunately I found some bugs related to this property having problem being read from config file. But it works great if you specify it programmatically:

IDictionary props= new Hashtable();
props[”timeout”] = 10000 ;//Wait for 10s in remote call.
//other properties like port etc.
HttpChannel chnl = new HttpChannel(props, .... ,....);

Originally from busy city of New Delhi, India, I did my M.S. in Comp. Sc. from Univ of North Carolina. After a brief stint with XP team at Redmond, I joined Microsoft Charlotte.

Now and forever married to my wife Khushbu, we both live in sunny southern Queen city Charlotte.

2. Passing custom Credentials:
If you want to specify the username, password at runtime and want to pass it with the remoting request. This has been different with .net 1.0 and .net 1.1.
.net 1.0 : All you want to do is set the credentials property on your HttpChannel and all remoting requests through this channel sink will use the specified credentials.
nICredential credObj = new NetworkCredential(userName,password,domain);
Properties["credentials"] = credObj;
HttpChannel hc = new HttpChannel(channelProperties,…, .... );