Date: Tue, 3 Oct 2017 08:25:34 +0100 From: Steven Hartland <steven@multiplay.co.uk> To: Andriy Gapon <avg@FreeBSD.org>, Ben RUBSON <ben.rubson@gmail.com> Cc: Freebsd fs <freebsd-fs@FreeBSD.org> Subject: Re: ZFS stalled after some mirror disks were lost Message-ID: <69fbca90-9a18-ad5d-a2f7-ad527d79f8ba@freebsd.org> In-Reply-To: <feff135a-3175-c5d0-eeb4-5639bb76789e@FreeBSD.org> References: <4A0E9EB8-57EA-4E76-9D7E-3E344B2037D2@gmail.com> <feff135a-3175-c5d0-eeb4-5639bb76789e@FreeBSD.org>
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On 03/10/2017 07:12, Andriy Gapon wrote: > On 02/10/2017 21:12, Ben RUBSON wrote: >> A sustained read throughput of 180 MB/s, 45 MB/s on each iscsi disk >> according to "zpool iostat", nothing on local disks (strange but I >> noticed that IOs always prefer iscsi disks to local disks). > Are your local disks SSD or HDD? > Could it be that iSCSI disks appear to be faster than the local disks to the > smart ZFS mirror code? > > Steve, what do you think? Yes that quite possible, the mirror balancing uses the queue depth + rotating bias to determine the load of the disk so if your iSCSI host is processing well and / or is reporting non-rotating vs rotating for the local disks it could well be the mirror is preferring reads from the the less loaded iSCSI devices. Regards Stevehome | help
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