Hi,
I have a Samsung SSD 850 EVO 4TB and under Linux I'm only getting
~240MB/s write speed. On Windows it's 490MB/s (yes, without cache).
The read speed is the same on both Linux and Windows, though. Both are
512MB/s.
Any ideas what this could be? It can't be a slow SATA link as read
speed are fine. And since write performance is fine on Windows so I'm
kinda stunned. Not sure how to proceed / debug this any further.
I'm testing with dd if=/dev/zero of=/dev/sdX bs=1M count=65536
conv=fdatasync. Results are similar without the conv=fdatasync. On
Windows I test with AS SSD.
Prior to testing I do a ATA security erase to make sure the SSD isn't
clearing any cells during the benchmark. (Previously I used blkdiscard
but then realized this would only 'mark' the cells as unused so it might
do the actual erasing in the background)
I tested this both with a 4.4.0 and 4.8.4 Linux kernel. Another
machines (different hardware) has the same results. All have a SATA III
interface.
Dmesg:
[ 4.741663] ata2.00: ATA-9: Samsung SSD 850 EVO 4TB, EMT02B6Q, max
UDMA/133
[ 4.752974] ata1.00: ATA-9: Samsung SSD 850 EVO 4TB, EMT02B6Q, max
UDMA/133
# cat /sys/block/sda/device/queue_depth
31
If you need anything else let me know. Any help is welcomed.
Regards,
Bram
--
To unsubscribe from this list: send the line "unsubscribe linux-ide" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
