Date: Wed, 21 Nov 2018 06:13:49 +0100 From: Matthias Petermann <matthias@petermann-it.de> To: freebsd-questions <freebsd-questions@freebsd.org> Subject: Performance considerations on vnode backed memory disks (throughput) Message-ID: <7394023e-d761-7264-84b7-bcf6f7c8e18f@petermann-it.de>
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Hello everybody, Yesterday I made an attempt and wondered a lot about the result. 1) Given is a system with two physical disks: The first disk is the system disk partitioned with GPT and formatted with UFS SU + J. The second disk is the data disk, also partitioned with GPT and formatted with UFS SU + J. Both partitions are about 1 GB in size. If I transfer a large file from the system disk to the data disk in this constellation, I get a throughput of 80 MB / s. 2) Then I extended the setup so that a memory disk is created and mounted on the data partition: root @ nas: / data # truncate -s 128G /data/vol1.img root @ nas: / data # mdconfig -a -t vnode -f /data/vol1.img md1 root @ nas: / data # newfs -U /dev /md1 root @ nas: / data # mount /dev/md1 /mnt If I transfer a large file from the system disk to the memory disk on the data disk in this constellation, I get a throughput of 20 MB / s. I am well aware that there must be an overhead. That this is so massive, however, surprised me. Which optimization options are available here? I would like to stay with sparse files. I would be very happy about some ideas or discussions on this topic. Best regards, Matthias -- Matthias Petermann <matthias@petermann-it.de> | www.petermann-it.de GnuPG: 0x5C3E6D75 | 5930 86EF 7965 2BBA 6572 C3D7 7B1D A3C3 5C3E 6D75
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