How does the backup media influence speed of imaging?

Discussion in 'backup, imaging & disk mgmt' started by SandyD, Sep 5, 2014.

  1. SandyD

    SandyD Registered Member

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    Just wondering how much longer it takes to do an image depending on the destination media used - I suppose using a different partition is fastest though not necessarily a good idea. A second internal drive is probably fast too but how does a networked drive, an external drive or usb stick increase the time?
    Has anyone some rough guidance and recommendation on what to avoid?
     
  2. TheRollbackFrog

    TheRollbackFrog Registered Member

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    Sandy, there's lots of things that guide imaging speed in a system.

    Since almost all imaging programs ('cept Windows Imaging) use data compression algorithms to keep the resultant images as small as they can be, the CPU speed can be a factor in overall imaging thruput, both in the imaging and restore processes. I have found that if the CPU speed is sufficient, the process is guided mostly by the slowest HDD/SSD involved in the imaging.

    Imaging to a target partition which is included on the same HDD as the one being imaged will always be pretty slow... and also very dangerous if you have a failure of that HDD. The main reason is that the poor disk positioning arm has to jump back and forth between the blocks being read and the blocks being written. HDD positioning is the slowest operation in a hard disk's life... it happens in many milliseconds rather than just a few or only in microseconds. Although this operation may be handy, if speed is a concern, it should be avoided. A 2nd internal SATA (or an eSATA external) drive would be the best choice for an imaging target.

    Networked drives, especially those accessed by a 10/100mb link (the most common HOME link other than WIRELESS) are quite slow. About the best thruput you can get with those is about 9mB/sec... which is about the same as a standard commercial USB FLASH DRIVE (UFD). A USB3 UFD (if connected to a USB3 port AND has decent WRITE thruput) can sometimes go as fast as a slower internal HDD at about 70mB/sec. When you mention "an external" drive above... most are USB connected. And even fast USB devices like an external drive can't do much more that 50% of the USB channel's speed (USB2=appx. 30mB/sec, USB3 real world = about 70mB/sec).

    Based on the above, an internal SATA (or external eSATA) HDD w/64mB cache would be your best choice for an inexpensive imaging SOURCE or DESTINATION HDD that will give you your optimum speed. Of course you can always blow those #s out of the water if both SOURCE and DESTINATION are SSDs instead.

    Just some thoughts...
     
  3. oliverjia

    oliverjia Registered Member

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    My suggestion: get an SSD that is at least 120GB as your OS+Program Files drive, and use a traditional HDD as your data storage. The speed difference is night and day.
     
  4. Robin A.

    Robin A. Registered Member

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    The SATA/USB chip and firmware used in the USB external disk can greatly influence the results. Also, the compression algorithm and the drivers used. Using USB 3.0 connections, I usually get 20 MB/s or less (that is, USB 2.0 speed) with Windows 8.1 drivers and my external Vantec USB 3.0 enclosures. And Linux drivers can be much faster in certain cases.
     
  5. SandyD

    SandyD Registered Member

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    Thank you - I did not realise that using a different partition on the same hd would slow down imaging but sure, I would not do it anyway due to the risk of total disk failure. I am using a second internal hd for regular backups but once in a while like to do additional safety backups and then need to connect either via USB or networked. I now understand the speed implications better. Still have not made the change to SSD but perhaps it's time .
     
  6. TheRollbackFrog

    TheRollbackFrog Registered Member

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    Sandy, Oliverjia's suggestion for an SSD will definitely speed up the general use of your system, but for imaging purposes, if you have a fairly quick CPU, the bottleneck will be either the SOURCE or DESTINATION storage element being imaged to/from. An SSD source will make only a minor difference in your imaging operation if the destination storage element is still an HDD (or Visa Versa). Only if both are SSDs will you see a big difference in speed.

    BUT... an SSD as your SYSTEM partition will make a HUGE difference in how your system will respond to your general use (almost like a newer faster computer)
     
  7. Brian K

    Brian K Imaging Specialist

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    Sandy,

    For what it's worth, some numbers. SSD to USB3 external HD.

    Writing image with compression..... 68 MiB /sec

    Writing image without compression..... 84 MiB /sec

    Copying an image file from SSD to USB3 HD..... 92 MiB /sec

    Copying an image file from SSD to SSD..... 234 MiB /sec
     
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