Date: Tue, 16 Jan 2018 15:55:54 +0100 From: Mark Martinec <Mark.Martinec+freebsd@ijs.si> To: freebsd-fs@freebsd.org Subject: Re: Reducing ZFS fragmentation by copying to larger disk Message-ID: <2bd5694830649fbe243daf533049d9d3@ijs.si> In-Reply-To: <alpine.GSO.2.20.1801151825420.18206@scrappy.simplesystems.org> References: <c2e1f7bd61bd080737e4b887e248d82a@ijs.si> <alpine.GSO.2.20.1801151825420.18206@scrappy.simplesystems.org>
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>> 1. attach new disks to a ZFS mirror and let them resilver, ... > > I don't think this would help with fragmentation at all. Thank you for confirming my guess! >> 2. use zfs send / receive to make a copy > > [...] It will even work within the same pool if there is enough free > space. Nice, this is helpful! Mark 2018-01-16 01:28, je Bob Friesenhahn wrote: > On Tue, 16 Jan 2018, Mark Martinec wrote: >> Having a ZFS filesystem with two 4 TB disks in a mirror that >> is 85 % full and apparently pretty much fragmented (scrubs >> or a resilver takes excessively long time), I intend to move >> its contents to a new pair of disks twice the size. >> >> My question is what method to use so that in the end the copy will >> be less fragmented: >> >> 1. attach new disks to a ZFS mirror and let them resilver, then >> remove the old disks (Would the copied content be any less >> fragmented, or perhaps would the added free space just >> relieve some of the problem?) > > I don't think this would help with fragmentation at all. > >> 2. use zfs send / receive to make a copy >> (is this any better than method #1 ?) > > This will work well as long as there is enough space to send to. It > will even work within the same pool if there is enough free space. > > Bob
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