Date: Sat, 23 Oct 2010 12:19:46 -0400 From: Adam McDougall <mcdouga9@egr.msu.edu> To: freebsd-fs@freebsd.org Subject: Re: ZFS: Parallel I/O to vdevs that appear to be separate physical disks but really are partitions Message-ID: <4CC30B22.7090507@egr.msu.edu> In-Reply-To: <20101023085832.GD1742@garage.freebsd.pl> References: <4CC215B4.3050607@nttmcl.com> <20101023085832.GD1742@garage.freebsd.pl>
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On 10/23/2010 4:58 AM, Pawel Jakub Dawidek wrote: > On Fri, Oct 22, 2010 at 03:52:36PM -0700, Eugene M. Kim wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> Greetings, >> >> I run a FreeBSD guest in VMware ESXi with a 10GB zpool. Lately the >> originally provisioned 10GB proved insufficient, and I would like to >> provision another 10GB virtual disk and add it to the zpool as a >> top-level vdev. >> >> The original and new virtual disks are from the same physical pool (a >> RAID-5 array), but appears to be separate physical disks to the >> FreeBSD guest (da0 and da1). I am afraid that the ZFS would schedule >> I/O to the two virtual disks in parallel thinking that the pool >> performance will improve, while the performance would actually suffer >> due to seeking back and forth between two regions of one physical pool. >> >> 1. Will ZFS schedule parallel access to different top-level vdevs? > Yes, ZFS stripes requests over all top level vdevs. > >> 2. If so, how can I suggest ZFS that certain vdevs should be treated >> not as separate physical disks but as partitions on the same physical >> disk? > Nope, that's not possible. > > Instead of adding next 10GB disk maybe it is possible to grow the one > you have? ZFS should be able to grow automatically. > What about creating a new 20gb "disk" then using zpool replace, export and import it to see the new size, and then retiring the old 10gb "disk"?
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