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Per Lindholm

Per Lindholm

  • Linux.com Member
  • Posts: 18
  • Member Since: 21 May 09
  • Last Logged In: 15 Oct

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  • Per Lindholm
    Linux MOOC ?
    With the popularity of MOOC's shouldn’t there be a Linux MOOC for beginners. Apart from the things you want to teach beginners. It could be fun for them if they express their creative side on assignments in the Libre office suit.
    Link to this post 27 Oct 13

    With the popularity of MOOC's shouldn’t there be a Linux MOOC for beginners. Apart from the things you want to teach beginners. It could be fun for them if they express their creative side on assignments in the Libre office suit.

  • Per Lindholm
    RE: Troubleshooting, limit speed of USB3 device on USB2 computer.
    Searched around a little and found the Supertalent USB 3.0 Express RC8. It has a SSD controller. Im happy to see that they also posted the USB2 benchmark. It seem to max out the USB2 port at over 35 MB/s even for small files which is what I wanted in the first place. So I guess you need to select more carefully among the cheap memorysticks even if you only have a USB2 port.
    Link to this post 16 Mar 12

    Searched around a little and found the Supertalent USB 3.0 Express RC8. It has a SSD controller. Im happy to see that they also posted the USB2 benchmark. It seem to max out the USB2 port at over 35 MB/s even for small files which is what I wanted in the first place. So I guess you need to select more carefully among the cheap memorysticks even if you only have a USB2 port.

  • Per Lindholm
    RE: Troubleshooting, limit speed of USB3 device on USB2 computer.
    I did the same tests with a 11.5GB file. RAID0 was not necessary, an ordinary volume with FAT or NTFS got the same results. Due to some update? I don't know. However the transfer of 1000+ music or image files were crippled, below 5MB/s. I don't have USB3 on this computer. Could you check the average speed you get when copying a folder with 1000+ images. Because of the many problems with flash memory sticks I wonder if its not better to abandon them as a recommended portable storage for larger devices. Now that we have SSD that are dropping in price couldn't we just buy SSD's in the form of a memory stick? I kind of liked but haven't tested those dual eSata/USB interface SSD that looks like memory sticks. If they perform well and get cheaper we could easily spread the use of Linux through teaching a detachable dualboot configuration.
    Link to this post 16 Mar 12

    I did the same tests with a 11.5GB file. RAID0 was not necessary, an ordinary volume with FAT or NTFS got the same results. Due to some update? I don't know. However the transfer of 1000+ music or image files were crippled, below 5MB/s. I don't have USB3 on this computer. Could you check the average speed you get when copying a folder with 1000+ images.

    Because of the many problems with flash memory sticks I wonder if its not better to abandon them as a recommended portable storage for larger devices. Now that we have SSD that are dropping in price couldn't we just buy SSD's in the form of a memory stick?

    I kind of liked but haven't tested those dual eSata/USB interface SSD that looks like memory sticks. If they perform well and get cheaper we could easily spread the use of Linux through teaching a detachable dualboot configuration.

  • Per Lindholm
    RE: Troubleshooting, limit speed of USB3 device on USB2 computer.
    [Possibly closer to a solution] For the fun of it I made a RAID0 volume of two 15GB partitions both on the 32GB USB3 memorystick. ( Use mdadm ). This seems to have solved the speed problem. I got a mean speed of 31MB/s write and 35MB/s read on the USB2 port. The file was over 4GB. Any thoughts why?
    Link to this post 15 Mar 12

    [Possibly closer to a solution]

    For the fun of it I made a RAID0 volume of two 15GB partitions both on the 32GB USB3 memorystick. ( Use mdadm ). This seems to have solved the speed problem. I got a mean speed of 31MB/s write and 35MB/s read on the USB2 port. The file was over 4GB.

    Any thoughts why?

  • Per Lindholm
    RE: Troubleshooting, limit speed of USB3 device on USB2 computer.
    If you look at the graph you see that write isnt stable. From 35MB/s down to 1 MB/s. What I would like to do is to limit the speed somehow to see at what speed it is stable.
    Link to this post 22 Jan 12

    If you look at the graph you see that write isnt stable. From 35MB/s down to 1 MB/s. What I would like to do is to limit the speed somehow to see at what speed it is stable.

  • Per Lindholm
    RE: Troubleshooting, limit speed of USB3 device on USB2 computer.
    I think its accurate the result with file copy gets the same mean speed. Could you help me with usbnet driver under debian squeeze. I don’t know how to get usb0.
    Link to this post 21 Jan 12

    I think its accurate the result with file copy gets the same mean speed. Could you help me with usbnet driver under debian squeeze. I don’t know how to get usb0.

  • Per Lindholm
    Troubleshooting, limit speed of USB3 device on USB2 computer.
    Since the USB3 memory sticks are really fast I expect they would maximize the speed of the USB2 port (480Mbit/s). I tried two sticks. With Disk Utility I got a sustained read speed of 40Mbyte/s but when I tried the write I only got around 10Mbyte/s. During write the speed frequently went down to very low after starting at 35Mbyte/s. I tried several of the latest distros and the result were the same. The plan was to try to set a hard limit on the speed to and from the USB3 device. I didnt find any such commands. Could I tunnel the USB traffic trough a simulated network device I then can traffic shape?
    Link to this post 21 Jan 12

    Since the USB3 memory sticks are really fast I expect they would maximize the speed of the USB2 port (480Mbit/s). I tried two sticks. With Disk Utility I got a sustained read speed of 40Mbyte/s but when I tried the write I only got around 10Mbyte/s. During write the speed frequently went down to very low after starting at 35Mbyte/s. I tried several of the latest distros and the result were the same.

    The plan was to try to set a hard limit on the speed to and from the USB3 device. I didnt find any such commands. Could I tunnel the USB traffic trough a simulated network device I then can traffic shape?

  • Per Lindholm
    RE: Similar way to secure smart phones and tablets?
    Yes as a last resort this should be possible. Like the uses for a liveCD the user should also be able to run the device in the secure mode. I hope this method has the affect of bypassing any installed apps that are bad. Running in the secure mode should not require you to reset the device, it could be that the user with his jail braked smartphone wants a secure environment to conduct money transactions.
    Link to this post 09 Mar 11

    Yes as a last resort this should be possible. Like the uses for a liveCD the user should also be able to run the device in the secure mode. I hope this method has the affect of bypassing any installed apps that are bad.

    Running in the secure mode should not require you to reset the device, it could be that the user with his jail braked smartphone wants a secure environment to conduct money transactions.

  • Per Lindholm
    RE: Similar way to secure smart phones and tablets?
    Thanks for the input. The problem with user acknowledgement is the rather large potential for mistakes. They have to know what there doing. What I meant is that you have essentially the same mobile OS twice. Both can be updated through a trusted system but user manipulation ( installing all kinds of apps ) is restricted on the secure system. This could also work as backup system if the user somehow trashes it.
    Link to this post 08 Mar 11

    Thanks for the input. The problem with user acknowledgement is the rather large potential for mistakes. They have to know what there doing.

    What I meant is that you have essentially the same mobile OS twice. Both can be updated through a trusted system but user manipulation ( installing all kinds of apps ) is restricted on the secure system. This could also work as backup system if the user somehow trashes it.

  • Per Lindholm
    Similar way to secure smart phones and tablets?
    I was going to do this as a blog post but I thought I get some feedback first. To see if its good enough to publish at all.:unsure: Similar way to secure smart phones and tablets. One way to move away from the problem of the malware ridden Windows platform was to run a Linux LiveCD. Why not use a similar approach to secure smart phones and tablets? The method works by bypassing any contaminated apps that have been installed on the user system by booting and running a minimal default system. Ideally the second system would be on a read-only media but a secure write protect system is perhaps good enough. Here the user can not install anything to compromise the system. To make it as simple as possible one can add a button to restart the device and to run the secure system, like a built in splashtop in a dualboot configuration. This method does not exclude the need for checking the applications in the appstore. However when security matters. When we do online banking and other money transactions we need to have a dedicated device. Be it a PC, smart phone or tablet.
    Link to this post 08 Mar 11

    I was going to do this as a blog post but I thought I get some feedback first. To see if its good enough to publish at all.:unsure:


    Similar way to secure smart phones and tablets.

    One way to move away from the problem of the malware ridden Windows platform was to run a Linux LiveCD. Why not use a similar approach to secure smart phones and tablets? The method works by bypassing any contaminated apps that have been installed on the user system by booting and running a minimal default system. Ideally the second system would be on a read-only media but a secure write protect system is perhaps good enough. Here the user can not install anything to compromise the system.

    To make it as simple as possible one can add a button to restart the device and to run the secure system, like a built in splashtop in a dualboot configuration.

    This method does not exclude the need for checking the applications in the appstore. However when security matters. When we do online banking and other money transactions we need to have a dedicated device. Be it a PC, smart phone or tablet.

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