Date: Sun, 28 Jun 2009 04:08:00 -0500 From: "James R. Van Artsdalen" <james-freebsd-fs2@jrv.org> To: Zaphod Beeblebrox <zbeeble@gmail.com> Cc: freebsd-fs <freebsd-fs@freebsd.org>, Rafael Caesar Lenzi <rc_lenzi@yahoo.com.br> Subject: Re: Adding more disk's on ZFS array Message-ID: <4A4732F0.3060802@jrv.org> In-Reply-To: <5f67a8c40906272318t2f27822dg3e30f7dc2345cb11@mail.gmail.com> References: <380571.31027.qm@web51002.mail.re2.yahoo.com> <cf9b1ee00906271527v1f3a8eb3g74b03ae6f58365e6@mail.gmail.com> <5f67a8c40906272318t2f27822dg3e30f7dc2345cb11@mail.gmail.com>
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Zaphod Beeblebrox wrote: > Not entirely true. For a RAID 0 stripe, yes, you can just add a disk. Be > clear, however, that existing data is not striped to that disk, but the new > disk is used for new data. > It's probably best not to think of a ZFS pool as a RAID 0 but instead as a set of vdev storage areas. All of the vdevs are candidates for new data writes, depending on free space, etc. > According to > documentation, each pool should be of the same RAID type. It doesn't, > however, specify that each set of RAID 5 disks should have the same number > of disks in it. This seems to mean that you could add a set of 3 disks > (raid 5) to an existing raid 5 array with 5 disks. > A pool is a set of vdevs, and different vdevs may be of a different type and have different characteristics. It is perfectly reasonable to create a pool with a single RAIDZ vdev and later add MIRROR vdevs, or any other kind of vdev. I prefer to use MIRRORs as the vdevs since it's easier to control exposure to various failure modes (power supply, enclosure, controller & disk firmware, etc).
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