Date: Wed, 28 Jan 2026 17:00:36 +0100 From: Matthias Apitz <guru@unixarea.de> To: freebsd-questions@freebsd.org Subject: external USB disk: 400MB/s transfer, but get only 40MB/s Message-ID: <aXoypNa5LYrleVfS@c720-1400094>
index | next in thread | raw e-mail
Hello, I did tests on two laptops (ASUS and C720) with different USB disks, and writing with # dd if=file of=/mnt/file bs=8m a big file of many GBytes, see below. The disk was always announced in /var/log/messages as a 400.000MB/s transfers devices by the driver, but the measured transfer was only between 40MB/s and 50MB/s. The file system on the USB disks was NTFS. Why is this? matthias Jan 25 10:57:41 ASUS-150 kernel: da0: <WD Elements 2620 1023> Fixed Direct Access SPC-4 SCSI device Jan 25 10:57:41 ASUS-150 kernel: da0: 400.000MB/s transfers 82594649636 bytes transferred in 2005.078575 secs (41192725 bytes/sec) Jan 25 11:57:26 ASUS-150 kernel: da0: <WD Elements 2621 1026> Fixed Direct Access SPC-4 SCSI device Jan 25 11:57:26 ASUS-150 kernel: da0: 400.000MB/s transfers 82594649636 bytes transferred in 1492.881431 secs (55325659 bytes/sec) Jan 25 13:08:13 c720-1400094 kernel: da0: <WD Elements 2621 1026> Fixed Direct Access SPC-4 SCSI device Jan 25 13:08:13 c720-1400094 kernel: da0: 400.000MB/s transfers 46271915961 bytes transferred in 1081.647154 secs (42779122 bytes/sec) -- Matthias Apitz, ✉ guru@unixarea.de, http://www.unixarea.de/ +49-176-38902045 Public GnuPG key: http://www.unixarea.de/key.pubhome | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?aXoypNa5LYrleVfS>