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My series 520 is slower than series 320 under Fedora 17

I just bought a series 520 SSD (240 GB) to replace my series 320 SSD (120 GB). I was expecting the speed when reading the ssd to jump from around 250 MBytes/sec to (hopefully) something at least twice that speed. To my surprise the series 520 was only ~130 MBytes/sec. This is observed under Fedora-17 using "dd if=/dev/sdb2 of=/dev/null bs=64k count=1000". The board is an older Asus M3A78T and has been happily running the 320 for 1.5 years.

series 320:

dd if=/dev/sda2 of=/dev/null bs=64K count=1000

1000+0 records in

1000+0 records out

65536000 bytes (66 MB) copied, 0.254144 s, 258 MB/s

series 520:

dd if=/dev/sdb2 of=/dev/null bs=64K count=1000

1000+0 records in

1000+0 records out

65536000 bytes (66 MB) copied, 0.494915 s, 132 MB/s

These number stay relatively constant, no matter how many seconds of transfer I do. Ditto for changing block size (bs=...) up to 1MByte. I see these numbers for the 520 when I attach it on the same SATA 3Gbit/sec link as the 320 or if I attach it on a new SATA 6Gbit/sec controller. I do see it attach at 3 Gbit/sec on the old controller and 6 Gbit/sec on the new controller. (So it isn't going down to SATA-1 speeds as far as the printf's I can see indicate.)

Is the 520 defective?

Added 2012-11-02: Is the 520 known to run the SATA interface differently than the 320? I've tried reading from a 1GByte file of highly compressible data (all zeros) and a file of random numbers for non-compressible data. Both times the transfer rates were essentially the same as above. The 520 is very consistently slow. Any ideas of what is going on here?

Message was edited by: Wolfgang Rupprecht

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Hi Wolfgang,

In our lab, the 520 series read speed was measured at 409 MBps.

The following was used to gather data:

Created a 64 GB partition for Writing/Reading & installed Fedora 17 on the remaining space of the SSD

Measured at various block sizes from 64kB to 1024kB

Wrote/Read various sizes from 2GB to about 34GB


Link speed

Customer (Write)

Intel (Write)

Customer (Read)

Intel (Read)


  1. 3.0 Gbps


141 MBps

258 MBps

273 MBps


  1. 6.0 Gbps


500 MBps

132 MBps

409 MBps

Let me know if you are still having issues.