Downloading fog/kernel/bzImage very slow

  • Hello,

    I’ve recently set up FOG and I’ve noticed it takes about 30 minutes to download fog/kernel/bzImage and the file after that (I don’t remember exactly what it is). I upgraded the BIOS, that doesn’t seem to have changed anything, since I read that might cause the problem.

    Here’s my setup:

    TestA ========== FOG Server — Client 1
    TestB ====/ ±- Client 2
    ±- Client 3
    ±- Client 4[/CODE]
    The === is our corporate network and — is our isolated network. Everything is gigabit networking.

    The FOG server acts as a NAT so that the clients can get out the corporate network. When I download bzImage using TFTP from the FOG Server to Client 1, it will download at about 60KBps. When I download the same file from the same server to TestA, it goes about 1-2 MBps. I thought it was a problem with the isolated network. But then I tried to download a different file: I downloaded a file (not using TFTP) from TestB to Client 1. And it went 1-2 MBps, too. So it seems that TFTP is only slow on the isolated side.

    First Test: TFTP bzImage from FOG Server to Client 1: 60KBps
    Second Test: TFTP bzImage from FOG Server to TestA: 1-2MBps
    Third Test: SMB (Windows shares) from TestB to Client 1: 1-2MBps

    What could possibly cause TFTP to be slow only for the isolated network?

  • hi,

    i took 10-15minutes to got away from this prompt (see attached file) what could be the reason?

    1. fogserver is a virtual machine from vpshere connected to 1gb switch port
    2. fog client is a phyiscal machine connected to 1gb switch port

    Though my imaging is sucessful, everything is fine except that it takes time on that mtftp connection…



  • Moderator

    I think you change the settings on the FOG server TFTP daemon and restart it. No changes necessary on the client.

    TFTP protocol is slow by design because it can only have 1 packet in transmission at a time. It sends data and waits for a response before sending the next packet. If there is something wrong with the network, it’s really noticeable using TFTP.

    I would suspect the NAT routing setup on the FOG server or possibly a problem on the switch that connects the FOG server to the clients.

  • I’ve discovered increasing the TFTP block size significantly increases the speeds on both sides (>10MBps from TestA, ~1MBps from Client 1). I’d be OK with just increasing the blocksize for TFTP in FOG on Client 1 instead of resolving the TFTP issue between Client 1 and FOG Server. Both would be nice.

    Does anyone know how to modify the block size for TFTP on the clients?