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  • Chewy Chong 4:35 am on June 27, 2004 Permalink | Reply  

    Reparse Point and EFS 

    The IBM consultants working with me today asked me an interesting question… “Why does EFS use reparse points?”

    Good question.  Did some research and here’s the answer:

    First problem, I didn’t completely understanding how NTFS reparse points work.  I always thought a reparse point as a location pointer to somewhere else.  If you use removable storage (RSS), your OS will start moving files you don’t use onto removable storage (such as a tape drive).  The file is now replaced with a reparse point.  When you access that reparse point, RSS will go and fetch the file for you.  OK… that makes sense.  But why then would EFS use reparse points?

    Well… the above explanation is sorta correct.  I’ve got the low-level stuff wrong.  Let us first identify the key players:

    1.      File system add-ons:  These add-ons provide additional functionality.  Examples are: Removable Storage, Encrypted File System.  They use reparse pointers to identify which objects on the file system should be processed by them instead of the file system.  

    2.      Reparse Point:  An attribute of a file or directory.  When the file system detects an action to a file or directory with a reparse point, it will look up the associated file system add-on then trigger the add-on.  

    In the case of RSS, a stub file is left of the file system with a reparse point referencing the RSS add-on.  When the file is access, the RSS add-on intercepts the call and performs the retrieval of the file from the removable storage device.

    In the case of EFS, the encrypted file is on the file system with a reparse point referencing the EFS add-on.  When the file is access, the EFS add-on intercepts the call and performs the encryption / decryption.

    That was probably not the best explanation in the world.  This TechNet article may do a better job.

    http://www.microsoft.com/technet/prodtechnol/windows2000pro/evaluate/featfunc/bestperf.mspx

     

     

  • Chewy Chong 5:48 pm on June 20, 2004 Permalink | Reply  

    Single Mode versus Multi Mode Fiber 

    I have never been able to remember what the difference is.  Ever since my old buddy back in the States (aka the networking expert) told years… I keep getting properties of the two mixed up.  Hopefully now I write this down, I’ll be able to remember it.  

    Single Mode

    -         Small light carrying core (d = 8-10 microns)

    -         Requires more powerful laser as the transmitter

    -         Expensive for short hauls

    -         Intended for long distance runs

     

    Multi Mode

    -         Larger light carrying core (d = 62.5 microns)

    -         Uses less powerful / LED laser (much cheaper) as the transmitter

    -         Cheap and good for short hauls

    -         Intended for short distance runs

     

  • Chewy Chong 7:50 am on June 18, 2004 Permalink | Reply  

    f(g(x)) and SimCity 

    This was an email I sent to my work’s infrastructure community.  Kinda cool stuff.

    Just read an awesome article regarding Microsoft and development.  Don’t worry… us TI folks will find it easy to understand and very insightful on the world of development.

    If you ever wonder why all that ‘automated memory management’ of programming languages (you as a developer don’t have to worry about allocating/un-allocating memory for your code) is all that special… consider this:

    f(g(x))

    How you would unallocated memory used by g(x) when its result will be used by function f?  Hmmm… I appreciate .NET (and other memory managed languages) slightly more.

    Another interesting tid-bit is the insane amount of time Microsoft has spent making sure new versions of their code was backwards compatible with old stuff.  Here’s a snippet:

    …heard about this from one of the developers of the hit game SimCity, who told me that there was a critical bug in his application: it used memory right after freeing it, a major no-no that happened to work OK on DOS but would not work under Windows where memory that is freed is likely to be snatched up by another running application right away. The testers on the Windows team were going through various popular applications, testing them to make sure they worked OK, but SimCity kept crashing. They reported this to the Windows developers, who disassembled SimCity, stepped through it in a debugger, found the bug, and added special code that checked if SimCity was running, and if it did, ran the memory allocator in a special mode in which you could still use memory after freeing it.

    The Microsoft developer working on this compatibility effort said:

    I get particularly furious when people accuse Microsoft of maliciously breaking applications during OS upgrades. If any application failed to run on Windows 95, I took it as a personal failure. I spent many sleepless nights fixing bugs in third-party programs just so they could keep running on Windows 95.

    Sounds interesting?  There’s a heck lot more where that came from.  Gosh… I love blogs.  Provides an insight that most of us wouldn’t get exposure to.  Read on:

    http://www.joelonsoftware.com/articles/APIWar.html

    The Microsoft developer I quoted above has a blog called ‘The Old New Thing’ at:

    http://weblogs.asp.net/oldnewthing/archive/2003/10/15/55296.aspx 

     

  • Chewy Chong 9:18 pm on June 12, 2004 Permalink | Reply  

    Ali Baba 

    There’s a kebab chain here in Sydney called Ali Baba (they sell stuff similar to the stuff we call ‘gyros’ back home).  Ever since I saw the name, its familiarity kinda bugged me.  Well… took me over 12 months to look it up but it did get done. 

    Do you remember a childhood story about some guy opening a cave with the words ‘open sesame’?  Ali Baba was the main character.  The full story can be found here: http://www.bartleby.com/16/905.html.  The Ali Baba chain’s website can be found here: http://www.alibaba.com.au.

     

  • Chewy Chong 7:13 pm on June 8, 2004 Permalink | Reply  

    Microsft ADS, DHCP, and Multiple Subnets (What a Mess!) 

    One of my good buddies back in the states asked the following in an email.  It is a good question and actually leads into the fundamental workings of ADS.

    Chris’s Question:

    Anyone successfully used ADS over a routed environment?

    We are having a problem connecting to an Automated Deployment Server via PXE across different subnets. I found some docs stating that I will need to enable some DHCP option specifically 66 (boot server) and 67 (boot filename).

    Anyone know the boot file name for ADS?

    Chewy’ Response:

    How far into the ADS PXE boot can you get with your current configuration? 

     

    The most immediate issue that I can think of (which you may have addressed already) is that:

    ·         DHCP related packets do not, by default, route outside of its subnet.

    ·         Requires DHCP relay agent (http://support.microsoft.com/?kbid=257579) (http://support.microsoft.com/?kbid=120932)

     

    From what I understand of the ADS PXE boot process, the DHCP server doesn’t actually provide the boot information to the client.  Yeah strange.  Here’s the low-down (people… feel free to correct me if I’m wrong).

     

    ·         What happens is that when the client puts a broadcast out for an IP address, the ADS PXE service hears the request along with the DHCP service running on the DHCP server. 

    ·         The ADS PXE service checks the requesting client’s MAC against the ADS Controller.  If the controller identifies the client has something to do…

    ·         The ADS PXE service responds to the DHCP IP request broadcast.

     

    Yup… the ADS PXE service puts out a DHCP packet.  The DHCP doesn’t actually do anything.  This is why the direct modifications to the DHCP scope options may not work.

     

    As a FYI:  This is why you have to run the adsdhcpconfig tool if both the DHCP service and ADS PXE service is running on the same box.

     

    Just incase though, I’m cc’ing our Australian resident ADS expert, Paul. 

     

    · &nbsp
    ;           Paul… anything you want to add?

     

    Hope this helps.

     

    Want to know more?


    Information on the types of messages DHCP takes in / puts out (eg DHCPDISCOVER):

    http://www.freesoft.org/CIE/RFC/2131/22.htm

     

     

  • Chewy Chong 6:30 pm on June 3, 2004 Permalink | Reply  

    Virtualizing a Physical Machine (P2V) and Microsoft Virtual Server 2005 

    Many months ago, I read that VMWare released a tool that will help move a physical machine onto a virtual machine in VMWare.  In other words, server consolidation (there will be physcially less servers) but still maintain the number of logical servers (the server will still show up on the network as a seperate entity).

    Here’s the cool part:

    Imagine being able to make snapshots of your physical server.  In the event the server fails, restore the snapshot onto a virtual one until you can fix the physical server.

    Imagine you have too many servers and the cost of maintaining all of them is way too much.  Maybe these servers are so old, you are worried you won’t be able to service them.  To make things worst, the services provided by the servers are mission critial but there’s no documentation on how it was setup.  Well, virtualize all these many servers into virtual machines and consolidate them onto a few physical machines. 

    Heck, you want to be able to make restore a machine in few minutes.  Run all your servers are virtual machines and the physical server craps out, ‘mount’ the virtual machines to another physical one. 

    Wow!  Talk about a cool idea.  Anyhow, MS is playing catch-up with VMWare.  This doesn’t mean the product isn’t good.  They’ve purchased the Connectix (spelling?) Virtual PC product a year ago and have been working on their new Virtual Server product.  I’ve actually stopped using VMWare and switched to Virtual Server.  I’m looking forward to this P2V tools when it gets released.  It will integrate with the MS ADS product (Automated Deployment Service).

    There is a blog all about virtualization:
    http://www.virtualization.info/

    They have more information about the VS P2V tool (announced at TechEd 2004):
    http://www.virtualization.info/200405archive001.asp#1085661206001

     

     

     

  • Chewy Chong 9:58 pm on June 2, 2004 Permalink | Reply  

    SMS 2003 and the Client Machine’s Computer Browser Service 

    It appears that in most situations, SMS 2003 is still WINS dependent and requires the Computer Browser service to be up and running.  Here’s a snippet from:
    http://www.microsoft.com/technet/prodtechnol/sms/sms2003/techfaq/tfaq01.mspx#XSLTfaqSection126124121120120

    You might be able to disable browsing and WINS if all of the following are true:

    Active Directory is implemented in your environment.

    The Active Directory schema is extended for SMS.

    All SMS clients are running the Advanced Client.

    You have no secondary sites in Windows NT® 4.0 domains.

    You have no secondary sites in a forest that is different from the forest of their parent site.

    You have no SMS 2.0 child sites.

    SMS is running in advanced security mode.

    This scenario is presumed to work, but operating in a non-WINS environment will not be fully tested until SMS 2003 SP 1.

    What is the computer browser service?
    http://support.microsoft.com/default.aspx?scid=kb;en-us;188001

     

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