[K12OSN] Tuning LTSP Performance

[Terrell Prude' Jr.]

Terrell Prude' Jr. wrote:
> Rob Owens wrote:
>> On Fri, Aug 29, 2008 at 11:41:42PM -0400, Terrell Prude' Jr. wrote:
>>  
>>> Robert Arkiletian wrote:
>>>    
>>>> 2008/8/29 Terrell Prude' Jr. <microman at cmosnetworks.com>:
>>>>  
>>>>      
>>>>> 2.)  If you're running LTSP of any sort, it's assumed that you're 
>>>>> running,
>>>>> at a minimum, a switched 10/100 environment (if not, then you 
>>>>> really should
>>>>> be!).  Unless A.) it's a managed switch capable of port mirroring, 
>>>>> and B.)
>>>>> you control said switch, you can sniff *your* traffic, but not other
>>>>> peoples.  To keep the Les Mikesells of the world happy, I'll point 
>>>>> out that
>>>>> yes, you could sniff the server if it's physically accessible.  
>>>>> But in God's
>>>>> name, I hope you have it secured physically so's to (largely) 
>>>>> prevent that!
>>>>>            
>>>> Please enlighten me Terrell. I don't understand how having access to
>>>> the server is a vulnerability in terms of sniffing packets. One must
>>>> have root access to be able to use a program like tcpdump or wireshark
>>>> to capture packets. So if they don't have root how can they sniff?
>>>>  
>>>>       
>>> Easy.  Say you're a "curious" kid.  :-)  Just insert your own switch 
>>> (yes, they're available on eBay) in between the server and its 
>>> network drop.  On your switch, mirror the port to your laptop 
>>> (laptop HD's are pretty big nowadays).  Boom, you've done it, and 
>>> no, it ain't that hard to do.  I do this sort of thing regularly at 
>>> work as part of my network engineer duties when troubleshooting 
>>> certain problems.
>>>
>>>     
>>
>> Or even easier (well, at least cheaper) is to throw a hub in between 
>> the server and the main switch.  A hub mirrors all ports -- at least 
>> that's how I understand it.  Anyway, I've tried it and it works.
>>
>> -Rob
>>
>>   
>
> Yep, that'll certainly do it, too.  The problem with that approach is 
> that it'd be much more noticeable from a performance standpoint.  
> Collisions will slow down LTSP to a crawl, and further, you'll slow 
> the server's NIC down to 100Mbps (Gig-E switches don't 
> exist--fortunately).  Therefore, naturally, someone'll investigate 
> sooner than if you used a managed 10/100/1000 switch to do the same 
> thing.
>
> --TP

'Scuze me...I meant "Gig-E *HUBS* don't exist--fortunately."  Geez....

--TP