Slow disk speed after few days

  • Hi since few days my disk slowed down. When I install ovm about week ago my disk works perfect and got transfer write/read about 110MB/s. Now I get not even half this value. The write values have dropped to about 25MB/s and read is about 80-100MB/s. Im tested this by dd command:


    Source Code


    Edit Source Code

    • root@media:/srv/dev-disk-by-label-Segate# dd if=/dev/zero of=pk count=1 bs=400M
    • 419430400 bajtów (419 MB, 400 MiB), 19,7161 s, 21,3 MB/s

    What is strange when I installed the fresh system on the second pendrive everything has returned to normal and the write speed is again within 110 MB/s.
    It looks like the speed of writing was limited somewhere in the system, but I dont know where. Im trying set max performance in disk options, but it did not bring any results.
    I would not like to re-install my system once a week, because that's not the point.


    My hardware Nettop nt-i1550:
    intel atom d2700 2/4 2.13 GHz
    4Gb DDR3
    Sagate Expansion 1TB USB 3.0
    16GB Pendrive USB 2.0 for system (with installed flash memory plugin)


    I hope someone can help me .
    Best regards, mix091.

  • Sagate Expansion 1TB USB 3.0


    Maybe just the usual 'joys' of using USB storage? Did you check dmesg output for anomalies? Do you know that USB3-A receptacles/connectors can be a real sh*t show due to the SuperSpeed contacts being laughable tiny? Did you check with lsusb and lsusb -t already whether the disk negotiated SuperSpeed or only Hi-Speed (most people call 'USB 2.0' even if that's just wrong)?

  • Thanks for replay,


    My usb hhd must work as USB 3.0 beacause read speed is correct:


    Code
    root@media:~# hdparm -t /dev/sdb1
    
    
    /dev/sdb1:
    
    
     Timing buffered disk reads: 392 MB in  3.00 seconds = 130.58 MB/sec


    Its not possible to reach 130MB/s on usb 2.0, I think. Only write speed is so low :(




    My dmesq and kernel log do not indicate anything strange.
    When I boot fresh install OMV my write speed on this HDD back to stable 100MB/s+.

  • Code
    Bus 007 Device 002: ID 0bc2:2322 Seagate RSS LLC
    ...
    /: Bus 07.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 5000M
    |__ Port 1: Dev 2, If 0, Class=Mass Storage, Driver=usb-storage, 5000M

    The above confirms that it's indeed SuperSpeed (USB Mass Storage and not UAS which is the correct way to deal with Seagate USB3 disks). Using hdparm to check disk speeds is never a good idea since this tool always reads from the outer tracks while HDDs use ZBR (Zone Bit Recording) and get slower once you put data on them: https://forum.armbian.com/topi…findComment&comment=15319 -- I would benchmark using iozone but this might require adding non-free Debian repos and then installing the iozone3 package first.


    In case this is an USB3 disk that is powered by the host (without an external PSU) you might run into the problem that underpowering occurs with writes and then the drive controller uses various strategies to deal with this (usually slowing everything down to lower consumption). I ran into this multiple times but am too lazy now to search the respective thread here with examples.

  • I thought that this might be because of the power supply, but it does not explain why everything works on a fresh installation.


    Here is my log from old system:


    Here is from fresh system:



    I do not notice any difference in kernel logs.
    My power supply unit for this nettop has 19V and 3.42A, what gives about 65W. I think it should be enought for power one external disk.

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