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what is wired LAN throughput to USB disk?

1749 Views 21 Replies Latest reply: Aug 21, 2007 4:24 AM by John Calhoun1 RSS
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odysseus Level 3 Level 3 (910 points)
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Aug 14, 2007 5:53 PM
The latest airport update is supposed to improve connections to a shared USB disk. I'm wondering what sort of throughput you are seeing from a wired ethernet connection on the LAN to the shared USB disk, in terms of read and write megabytes/second. Is the throughput comparable to an average NAS, i.e. 3-5 megabytes/second?
PowerBook G4/1.67 GHz, Mac OS X (10.4.10), 7200rpm 100 GB HD, 2 GB RAM
  • sfineone Calculating status...
    Currently Being Moderated
    Aug 14, 2007 10:17 PM (in response to odysseus)
    I did an informal test.... I have a 500GB SATA disk in a generic external enclosure. Formatted HFS+
    Test is as follows:
    Drag a folder of 35 files totalling 4.76GB from external disk to internal disk.
    USB connected: 200s or 23MB/s
    Wireless N: (airport right next to mac): 776s or 6.1MB/s
    Wired gige: 526s or 9.05MB/s

    This was very dissapointing... on the recommendation of the guys at the Apple store, I bought the new airport extreme to hang some disks on it. I am considering returning it, and buying a true NAS. Many of them show better throughput in the reviews.
    I don't know where you found the average NAS speed to be 3-5MB/s that seems very slow. macuser shows a Lacie Ethernet big disk running at 50MB/s on gige and 42 on USB. see review at
    http://www.pcpro.co.uk/macuser/reviews/119156/lacie-ethernet-big-disk.html
    New iMac, Mac OS X (10.4.10)
  • sfineone Level 1 Level 1 (0 points)
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    Aug 15, 2007 6:48 AM (in response to odysseus)
    Thanks, but don't know that I agree...
    take a look at
    http://www.smallnetbuilder.com/component/option,com_nas/Itemid,190/chart,12/

    I still think 9 MB/s is on the very low end of performance.
    But, you are correct, the Airport wasn't meant to be a hi performance NAS.

    Thanks... will have to think this one through a little bit.
    Maybe I will just build my own!
    Imac G5, Mac OS X (10.4.10)
  • Jayster68 Level 1 Level 1 (5 points)
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    Aug 15, 2007 9:51 PM (in response to odysseus)
    You must be using the 100 Mbps Airport Extreme. I just picked up the Gigabit model and I'm getting 16-17 MB/sec. While not super fast it's pretty good.

    I think the speeds you are seeing is right in line with a 100 Mbps network.
    iMac Core Duo, Mac OS X (10.4.10)
  • Jayster68 Level 1 Level 1 (5 points)
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    Aug 16, 2007 7:19 AM (in response to odysseus)
    my mistake, read the post wrong. I'm not sure of the wireless speeds as I don't have a N client to test it with, I was using the wired gigabit to obtain those speeds.

    So it looks like the network speed is the limiting factor until you use gigabit then USB 2.0 is limiting performance.

    Over all I'm very happy with the performance, I didn't expect it to be as fast as it is. My plan was to simply use it as a back up drive, any files I need fast access to I will just use Firewire. As it's not really intended to be a high end NAS
    iMac Core Duo, Mac OS X (10.4.10)
  • sfineone Level 1 Level 1 (0 points)
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    Aug 19, 2007 11:01 AM (in response to Jayster68)
    Hi... I was using GigE... 4 foot cable from mac right to airport. ifconfig confirmed 1000 baseT connection.

    What disk setup are you using? Brand/Model etc?
    While I agree that macuser tests were not achievable, I still expect USB2.0, which is a 480Mb/s interface to be faster than
    9MB/s. If the USB2.0 disk plugged in directly to the mac is 23MB/s and the GigE is over 2x the USB speed, even with protocal overhead, the airport should be able to do better than 9. Just my opinion.....

    I am looking at wired speeds, the N doesn't bother me so much as I will be wired when I do backups as well.

    Not trying to be controversial, just trying to set my expectations.
    Imac G5, Mac OS X (10.4.10)
  • Barry Brown3 Level 1 Level 1 (5 points)
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    Aug 19, 2007 12:24 PM (in response to odysseus)
    You'll never get 480mbps from a USB-attached disk, even directly connected to the Mac. The disk drive itself simply can't pump out the bits that fast.

    Unfortunately, hard drive manufacturers (such as Seagate) don't publish the internal disk transfer rate for consumer ATA and SATA drives. But they do for server SCSI and SAS products. The internal transfer rate is a measure of how fast the bits can be read off the disk platters. Seagate's Cheetah line of 10,000 RPM SCSI disks have a published sustained transfer rate of 39 to 80 Mbytes/sec, which is likely to be much higher than for the consumer-grade SATA and ATA drives.

    Compare that to 480mbps, which translates to a raw speed of 60 Mbytes/sec, which seems to fall in the middle of the SCSI transfer rates. But a statistical analysis of the USB protocol shows that actual USB speed is only about 10-20% of the raw speed, due to the overhead and delays inherent in the protocol. This puts USB 2.0's top speed at around 12 Mbytes/sec, more or less.

    Analysis of the USB 1.1 protocol:
    http://www.edn.com/archives/1996/102496/df_01.htm

    Speed tests of USB 2.0 and Firewire:
    http://www.digit-life.com/articles/usb20vsfirewire/

    USB 2.0's raw speed of 480 mbits/sec was carefully chosen to appear to be faster than Firewire's 400 mbits/sec, but theoretical analysis and practical tests show the actual throughput is much less. That consumers believe USB 2.0 to be faster is a testament to the power of marketing and branding.
  • Barry Brown3 Level 1 Level 1 (5 points)
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    Aug 19, 2007 10:41 PM (in response to odysseus)
    Certainly no better than a directly-connected USB device. The network will add a bit of latency, but the bottleneck is the USB connection, especially if gigabit Ethernet is being used. Ethernet was designed to move lots of the same kind of data at the same quick speed. The overhead is low. But USB was desigend to move lots of different kinds of data at different speeds. Keyboards, mice, hard drives, DVD-R drives, scanners, printers -- they all have different data transport needs. In order to accomodate their needs, there's a lot of flexibility in USB, and that leads to more overhead in the protocol.

    100Base-T will move data at just under 100 mbits/sec, or about 12 mbytes/sec -- roughly the same speed as USB. When gigabit ethernet is used, data flows through the network at 10x the speed of 100Base-T, but USB is still the bottleneck.
  • Jayster68 Level 1 Level 1 (5 points)
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    Aug 20, 2007 12:55 PM (in response to Barry Brown3)
    "This puts USB 2.0's top speed at around 12 Mbytes/sec, more or less."

    Barry your kidding right ? the link you supplied is benchmarked of a system with a 566 MHz Celeron CPU on Windows 98. Plus 12 Mbytes would only equal 1.5 MBps. There is a difference in Mbps & MBps

    USB 2.0 uses the CPU far more then Firewire so using a slow CPU with win 98 would degrade performance considerably. Look at newer benchmarks on sites like Toms hardware and you will see USB 2.0 drives often reaching 30 MB per sec and some slightly faster. This is still much lower then the 480 Mbps (or 60 MBps) that USB 2.0 is rated at. So it often performs around 50% of the rated spec not 10 - 20%

    I tested again and was still able to get 16-17 MBps with 1000 Mbit connection. I'm testing with a 2.0 Core Duo iMac with the gigabit AES and a WD 7200 RPM hard drive in a Adaptec enclosure. I'm using a 1.2 GB movie to transfer, Using a lot of smaller files did lower performance to around 14MBps write but did not hurt the read speed. This same drive benchmarks at 28 MBps when hooked directly to the computer, so the bottle neck is probably the CPU the AES is using as both the network and the drive can run faster then 16 MBps. However with that being said, those speeds are very respectable for a $179 wireless N router / print server / NAS
    iMac, Mac OS X (10.4.6)
  • John Calhoun1 Level 1 Level 1 (35 points)
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    Aug 20, 2007 1:43 PM (in response to odysseus)
    Not to dog pile or side track to ongoing conversation....but I'm another displeased gigabit AEBS user concerning data throughput speeds on the AirDisk attached drive.

    I've been getting 1.16 Mbps to 2.36 Mbps using GigE and CAT6 equipped Macs. Now transfer from Mac to Mac, both on GigE, I get around 200 Mbps.

    I'm still trying to tweak my network because surely I can get better throughput speeds than what I'm getting. I agree with the scientific differences between UBS and FW. However - a couple of wrenches I'll throw out for consideration:

    1. Will having multiple partitions on the hard drive affect read/write speeds?

    2. What about format - HFS versus FAT32. If the setup is suppose to be quasi-NAS - then which one for speed?

    3. What about placing the AEBS as a bridge to another router that handles the WAN and DCHP duties? By allowing the AEBS act as an extension - will data throughput on the AirDisk improve? See pg 36 on the Designing AiPort Networks manual.

    So - I guess I made the conversation worse...sorry.

    jc
    MBP 2.16 CD, 2GB | 17" iMac 2.0 GHz G5 PPC, 1.5GB | MacBook 2.0 GHz C2D, 1GB, Mac OS X (10.4.10), 30GB 5G, 4GB 1G Nano, & 20GB 4G iPods
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