Date: Mon, 13 May 2019 11:07:32 +0000 From: bugzilla-noreply@freebsd.org To: fs@FreeBSD.org Subject: [Bug 237807] ZFS: ZVOL writes fast, ZVOL reads abysmal... Message-ID: <bug-237807-3630-BGc0TSbTLP@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-237807-3630@https.bugs.freebsd.org/bugzilla/> References: <bug-237807-3630@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D237807 --- Comment #3 from Nils Beyer <nbe@renzel.net> --- (In reply to sigsys from comment #2) the benchmark tool is completely sequential as it is a simple: dd if=3D/dev/zvol/morsleben-grube2/test of=3D/dev/null bs=3D1M ^C 375390208 bytes transferred in 15.330245 secs (24486902 bytes/sec) whereas the ZVOL has been filled before with random data using: dd if=3D/dev/urandom of=3D/dev/zvol/morsleben-grube2/test bs=3D1M ^C 8544845824 bytes transferred in 77.684268 secs (109994546 bytes/sec) "primarycache" and "secondarycache" are disabled for that ZVOL to get real = read speeds... Now, I've followed your advice and tried two identical instances of "dd" reading from the ZVOL. And you are right, I get twice the throughput: 40MB/s now. It still is abysmal if you ask me, but okay... The slow read throughput also exists via the iSCSI connection from a Windows Server (the ZPOOL "morsleben-grub2" is a backup target). So I have to convi= nce the Microsoft iSCSI initiator somehow to create more concurrent reads. Thank you for the pointers... --=20 You are receiving this mail because: You are the assignee for the bug.=
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