Gigibit switch

Discussion in 'Mac OS X Server, Xserve, and Networking' started by Danmickread, Dec 3, 2012.

  1. macrumors newbie

    Joined:
    Nov 12, 2012
    #1
    hi i recently bought a netgear gigabit switch to connect my imac and linkstation live ls-chl at gigabit speeds. They are both connected at 1000Mb/s but i only get transfer speeds of around 12MB/s according to activity monitor and i used to get 7MB/s with a 100Mb/s ethernet connection so not even double. Why is this and what should i be able to expect to get.

    I found the settings for frame size in the web setup interface for the NAS and when i increased this it just made it slower.

    Any suggestions?

    Thanks

    Dan
     
  2. macrumors 6502

    Joined:
    Dec 9, 2005
    #2
    How long have you had it and how full is the drive? Possibly fragmented and struggling because of the disk? Possible other disk issues (i.e. dying?!).
     
  3. thread starter macrumors newbie

    Joined:
    Nov 12, 2012
    #3
    It can't be fragmented it hardly gets used. I've had it a few years and its got about 900 gig out of 1000 left.
     
  4. r0k
    macrumors 68040

    r0k

    Joined:
    Mar 3, 2008
    Location:
    Detroit
    #4
    Linkstation and other low-end NAS might come with gigabit ports but it's very likely they don't perform well enough to fully use the thing. I have a low-end Synology disk station. It runs DSM 4 (Linux variant) on an ARM processor and I installed a WD Caviar "green" drive which is known to be slow. For me the big win is the ability to run an NAS for 18 watts peak and 6 watts standby. I have never experienced stuttering watching 2 simultaneous streaming SD movies off the thing. I never stream HD because it's a waste of bandwidth and disk space and SD looks fine on my 55 in LG screen.
     
  5. macrumors newbie

    Joined:
    Jan 26, 2012
    Location:
    Michigan
    #5
    Is your switch connected to a wired/wireless router?

    Most of your basic switches are layer 2 only where as IP traffic from one device to the next on your network is layer 3. In this case, all traffic from one device to another on your network has to go out the sending device, through the switch, to the router to figure out where the receiving IP is, back through the switch and finally to the receiving device. You are limited by the throughput of your switch (keeping in mind the data goes through the switch twice) and the router (which is normally the bottleneck) as well as the read/write speeds of your hard drives (these usually run at about 150MB/s for a 7200RPM drive).

    Just because you have a gigabit switch doesn't mean you are going to get gigabit speeds. The sad reality is that most marketing departments know that consumers are stupid and will buy the cheapest product with the largest numbers on it. There are many more important factors in your network than port speed!
     
  6. thread starter macrumors newbie

    Joined:
    Nov 12, 2012
    #6
    Appreciated but should I expect more than 12MB/s?
     
  7. dazey, Dec 3, 2012
    Last edited: Dec 3, 2012

    macrumors 6502

    Joined:
    Dec 9, 2005
    #7
    I think its fair to say you should. You should try and find other users of the linkstation device to see if they all do this or whether yours has 'issues'. I seriously doubt your switch has anything to do with the issue (you could test for this by connecting the link station direct to your iMac with a ethernet cable)

    Oh, and a point of reference. I am busy transferring a load of data onto a WD Caviar Green (so not a quick drive), connected via a standard domestic grade gigabit router/switch linking two macs. I get average transfers speeds of around 50-60MB with a peak of 105MB (I have no idea how it hit 105, possibly was transferring something to the servers SSD instead)
     
  8. macrumors regular

    Joined:
    Sep 24, 2011
    #8
    What are you doing when you get the 12 MB/s speed? Playing a video, transferring a large file. It could be that is all whatever you are doing needs. Try transferring a very large file, at least 1 Gigabit, and see where it peaks.
     
  9. macrumors demi-god

    mmomega

    Joined:
    Dec 30, 2009
    Location:
    DFW, TX
    #9
    12MB/s is 100Mb/s, are you verifying that you are actually connected at 1000?

    Most of those switches have 2 LED's on the connection end, 1 LED means 10/100Mb/s and 2 means Gigabit.

    Also did you change to a different ethernet cable or are you using the same?

    If you are maxing out gigabit you can expect right around 120MB/s.

    I bought a cheap 24port Trendnet Gigabit switch and every computer connects at 1000, I'm using CAT6 that I ran through the house. If my switch will handle it, surely a Netgear would.

    Which switch did you buy exactly? If you have the model numbers handy
     
  10. thread starter macrumors newbie

    Joined:
    Nov 12, 2012
    #10
    I am transferring a large file. 6 gig.

    ----------

    It's a net gear gs 108 I have read good reviews.

    Perhaps I will try connecting nas straight to mac and see if that improves things.
     
  11. macrumors member

    Joined:
    Sep 3, 2010
    #11
    Um, no. If your two devices (Mac and NAS) are on the same LAN, then the arp cache in the IP stack on both devices will know each other's ethernet MAC address. Communication will always be direct and your switch doesn't need to know the IP addresses. It's smart enough to know which MAC addresses are connected to which ports (that's the whole point of a switch). The reason a router works at all is because it answers arp requests for IP addresses not on your LAN (assuming it's configured with a proper route). The router takes those packets and forwards them out to the network on the other side of the router. If it gets a reply back then all of the magic worked and your computer is able to talk with that IP address. Your switch doesn't care, nor should it.

    I have the GS108 also and I love it. I can sustain 50-60MB/s with it on my network. I suspect I'm now IO limited at my computers, not the switch.
     
  12. macrumors 6502

    rpg51

    Joined:
    Jul 4, 2012
    #12
    Reading with interest. Does anyone know the answer to the question above - will Cat 5 ethernet run at gigabit speeds? I have Cat 5 going to a room in my house and I'm wondering if I need/should upgrade it. It would be a pain to do.
     
  13. thread starter macrumors newbie

    Joined:
    Nov 12, 2012
    #13
    ok heres an update.

    i connected my nas straight to my computer with a cat 5e cable and increased my mtu on mac and nas to 9000 and the speeds went up a bit to 15-17MB/s i guess this is the best im gonna get is it.

    Thoughts please?

    Dan
     
  14. macrumors 6502

    Padaung

    Joined:
    Jan 22, 2007
    Location:
    UK
    #14
    After seeing this thread, I did some Googling and this page came up and might be of use to you too. It was a handy explanation (in layman's terms, which was fine for me!)

    My home gigabit network runs at a speed of 36MB/s, which going my what that article says, is probably the max speed of the hard drive in my laptop.
     
  15. thread starter macrumors newbie

    Joined:
    Nov 12, 2012
    #15
    What article?
    I'm sure my IMac hard drive can handle more than 17MB/s
     
  16. macrumors 6502

    Padaung

    Joined:
    Jan 22, 2007
    Location:
    UK
    #16
  17. macrumors regular

    Joined:
    Nov 15, 2002
    #17
    To the best of my knowledge you need to be running Cat-5e cables at a minimum, Cat-5 is not sufficient.

    As others have pointed out 12MB/s is 100Mbit - sounds more like you're saturating a 100MBit link rather than getting pathetic performance from a Gigabit one.
     
  18. macrumors member

    Joined:
    Feb 17, 2012
    #18
    I'm using a Synology DiskStation with a couple macs and connected via a Netgear Prosafe 24 GE switch. I also thought I should be seeing higher speed transfers between my macs and the diskstation. One thing I did that made a big difference was to make sure the GE interfaces on the macs are set up as manual config/ 1000baseT and full-duplex. I recall that by default the duplex setting was set to one of the energy efficient options. After I changed it to "full-duplex" I was getting much better throughput.
     
  19. macrumors 6502a

    Joined:
    Oct 29, 2008
    #19
    It is most likely just the NAS being slow. The Linkstation is a pretty cheap device.

    Anyway if you have another computer hook it up to the network in place of the Linkstation and test the transfer speed.
     
  20. macrumors regular

    Joined:
    Jan 12, 2009
    Location:
    London
    #20
    to test the switch, use iperf/jperf rather than transferring a file

    iperf/jperf are not disk bound...
     
  21. macrumors member

    Joined:
    Sep 3, 2010
    #21
    Your GS108 supports Jumbo Frames up to 9k. You could probably still use it.
     
  22. macrumors newbie

    Joined:
    Dec 6, 2012
    #22
    Hi I know I'm late to the party on this one but the above comment is only right if the two devices communicating aren't within the same subnet. The IP session is active between the NAS and the Computer, 'below that' there is an switched Ethernet session thru the switch in a pseudo-point-to-point fashion.

    As for the speed issues you're seeing for the most part it is likely the speed of the hard disk, however (and to quote Ben Goldacre) "it's a little bit more complicated than that".... things to consider:

    1 - Spinning hard disks are awful for writing data in an orderly fashion, they're spinning very quick and write data to the next available place. Imagine a teenager walking into their room and discarding their jacket in the first available floor space. This makes for sub-optimal reading and writing from day 1.

    2 - The theoretical maximum data speeds of hard drive controllers are simply that... theoretical they aren't for the most part achievable in the real world. Hardware manufacturers place the HD controllers 'south' of mediation chips like southbridges which in turn don't have the facility to 'talk to the cpu' at even the speed the HDD controller abd HDD can sync.

    3 - Network controllers tend also to 'live' off a southbridge (SB) or similar hence the data path from the disk to the network goes from the HDD controller, up thru the SB, gets processed, down thru the SB and on to the network. Classic data tromboning very inefficient and encountering multiple 'bottlenecks'.

    4 - Ok finally out of the computer/NAS now, cheap/home network switches (whether they say Gigabit or not) are made cheaply, this often means that each Gigabit port on the switch shares the Gigabit speed to the switch 'backplane' with a cluster of other ports (for example in a Cisco Catalyst 3750v2 24 Gig port switch there is a 6-to-1 port-to-backplane ratio and they cost $6k upwards!). So more than likely the actual potential thru put of your switch is maybe a Gig divide by 4 or something similar, there's a saying "you get what you pay for" it's for the most part true with computer equipment too.

    These are just things to consider, the jumbo framing idea should work as it increases the data payload to framing overhead ratio...
     
  23. macrumors 6502

    Joined:
    Dec 9, 2005
    #23
    This is what the specifications require but bear in mind that the specs allow for gigabit to run 100metres on cat 5e. You are likely to be able to run gigabit over standard cat 5 over the kind of distances that you get in homes without issue (unless you live in a mansion). If you are procuring cable now though, 5e is the minimum to look at.
     
  24. macrumors regular

    Joined:
    Oct 10, 2011
    #24
    The fastest I have seen is 80MB/s. Copying 1 a 1GB file from OS X Server. I was copying to /dev/null on the client so there was no slow down on the writing side of things. Also I loaded the file into RAM on the server to get the best copy speed.

    Normally i expect to see transfer speeds of 50MB/s over GB Ethernet.


    B
     
  25. macrumors regular

    Joined:
    May 12, 2010
    #25
    As long as two computers are in the same broadcast domain, which they are if they are on a local network, then traffic doesn't need to be routed between them at layer 3. This is why there is a subnet mask - the NIC will compare the subnet mask with the network address and depending on the result will attempt to hit the default gateway in order to route the traffic. In this case there is no need so it will use ARP to get the traffic to the appropriate destination.
     

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