I have 2 intel 520 series, the SSD's were used, the data written and read is about 2TB on the first SSD and 4TB on the second one.
I've did an ATTO benchmark, and i know in the past the performance was higher, now look at this...
And look at the total LBA written and read, this could influence an ssd performance ?
And also, i'm using intel RST 11.6, and both SSD's are secure erased fresh with parted magic, as you can see at the unsafe shutdown count the number is high, so i've secure erased them many times before to install windows 8.
I'm using windows 8, and i've tested ATTO in windows 7 as well but ti's the same performance.
If anyone knows or haves an 520 series, please reply. Why the read is that slow on 4.0 and 8.0, is normal ? If i change the position of the SATA cables i could get better performance ?
And the strange thing is that i bench them on empty data i get the same speeds.
The write speed being faster than read speed is strange and not normal.
Have you run the SSD Optimizer on your 520's in the Toolbox?
What does the Toolbox show your 520's health as? Even with 4TB writes, another SMART value looks like the health would be 100%. Did you try running at least the Quick Diagnostic Scan on your 520's?
Information about your PC is needed, what mother board do you have? What SATA mode are you using and set to in the BIOS? I have no idea what SATA ports your 520 is connected to, so can't comment on that.
You should try running AS SSD benchmark on one of your 520's, and post a screenshot of the results. It's a free program, just Google it and download.
The unsafe shutdown count seems to have a bug with all 520's, normal restarts of the PC are usually counted as an unsafe shutdown. That is nothing to worry about.
Your Uncorrectable Error Count seems high, but usually clears up after a reboot or two, have you done that lately?