Date: Tue, 29 Nov 2016 14:50:23 +0000 From: Steven Hartland <killing@multiplay.co.uk> To: freebsd-stable@freebsd.org Subject: Re: Sandisk CloudSpeed Gen. II Eco Channel SSD vs ZFS = we're in hell Message-ID: <4a2d4074-3455-5edb-4682-f1d6b82022fa@multiplay.co.uk> In-Reply-To: <583D74FE.8040402@norma.perm.ru> References: <345ed411-1430-50f7-6887-5ac00d259fd9@norma.perm.ru> <553eff7a-0cd5-eea9-4acd-4bc770fa1baf@multiplay.co.uk> <583D74FE.8040402@norma.perm.ru>
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On 29/11/2016 12:30, Eugene M. Zheganin wrote: > Hi. > > On 28.11.2016 23:07, Steven Hartland wrote: >> Check your gstat with -dp so you also see deletes, it may be that your >> drives have a very slow TRIM. >> > Indeed, I see a bunch of delete operations, and when TRIM disabled my > engineers report that the performance is greatly increasing. Is this it ? > Yep sounds like the TRIM on the disk is particularly poor. You can download, compile and run http://blog.multiplay.co.uk/dropzone/freebsd/ioctl-delete.c You can run with: ioctl-delete <device> <startblock> <blockcount> This will time and give you performance info with regards to delete requests. It uses raw BIO_DELETE commands to the device so eliminates filesystem latency (don't run on a device that's in use). You'll likely want to put some data on there though as often FW eliminates the delete if it will have no effect e.g. dd if=/dev/random of=<device> bs=1m count=20480 Regards Steve
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