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My SSD Samsung 840 was used as OS drive for a Windows 7 based machine.
I want to use it now as external SSD drive under Ubuntu.
I formatted it with Gparted to remove recovery partitions of Windows (that were unallocated).
I have noticed that now the disk is much slower than before formatting.

What do I have to do ?

Thanks !

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    You mean you connected it with USB to your machine?
    – falconer
    Jan 24, 2014 at 23:14
  • Yes that i what I did.
    – Gonzague
    Jan 25, 2014 at 21:43

1 Answer 1

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If you connect your SSD with USB to your computer you are limited by the USB bandwidth.

A Samsung 840 SSD can do ca. 500MB/sec read, the USB 2.0 has a theoretical limit of only 60MB/sec but practically it can only do about 30MB/sec. This is likely your problem, USB2 is just too slow.

With an USB3 port (and USB3 cable and USB3 capable casing) you should be able to utilize most of the speed of your SSD even externally. (or with an eSATA port, or something other which is faster than USB2.)

Also if your drive is formated to NTFS it will be significantly slower on linux than on windows, because the linux NTFS driver is a slower one. This is because the NTFS file system is proprietary, and Microsoft didn't release the specifications of it, so the guys who wrote the linux driver had to reverse-engineer the file system. If you swtich to a linux native file system, like ext4, you will likely get better performance.

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  • For copying files from internal SSD to the external SAMSUNG SSD connected with USB 3.0 port, it averages 130 MB/s, I think I got more (around 180 MB/s) before formatting the Samsung SSD. The speed indicator in Ubuntu keeps lowering until it reaches that speed (starts at around 200 MB/s). BTW, what is the correct format file to use to format a SSD drive as external or secondary non system disk ? NTFS or something else ?
    – Gonzague
    Jan 26, 2014 at 16:25
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    @Gonzague Is this a 128GB one? It has exactly 130MB/sec write speed at max. See it in this doc. If you use only linux then stick with ext4. If you also need windows access for the SSD use NTFS. Also note that if you use NTFS it will be slower on linux, because the NTFS file system is proprietary, the linux drivers are only reverse engineered and because of this NTFS drives are slower on linux than on windows. So if your drive is currently NTFS, that could cause also a slowdown on linux.
    – falconer
    Jan 26, 2014 at 16:40
  • it is a 500GB, and I used NTFS. Ok, I will format it in EXT4. Thanks.
    – Gonzague
    Jan 26, 2014 at 18:57
  • Ok, switched to EXT4, and now it is much faster ! Thanks !
    – Gonzague
    Jan 26, 2014 at 19:49

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