From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bram Matthys Subject: Write performance 50% compared to Windows Date: Tue, 01 Nov 2016 11:37:42 +0100 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.vulnscan.org ([149.210.174.15]:48230 "EHLO mail.vulnscan.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1168776AbcKALUg (ORCPT ); Tue, 1 Nov 2016 07:20:36 -0400 Received: from mail.vulnscan.org ([149.210.174.15]) by mail.vulnscan.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c1WRq-00037p-5T for linux-ide@vger.kernel.org; Tue, 01 Nov 2016 11:37:42 +0100 Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: linux-ide@vger.kernel.org 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