Date: Sun, 10 Apr 2011 01:32:58 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Chris Telting <christopher-ml@telting.org> Cc: freebsd-questions@freebsd.org Subject: Re: ZFS Striping and Optimizing Capabilities Message-ID: <20110410063258.GA10022@dan.emsphone.com> In-Reply-To: <4DA131BD.3030805@telting.org> References: <4DA131BD.3030805@telting.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In the last episode (Apr 09), Chris Telting said: > Just a few questions about what ZFS actually does. So if anyone has > intimate knowledge about ZFS's implementation on Freebsd I'm sure I and > others would appreciate the answers. > > When you add a second and or thrid drive/partition to a zpool I'm assuming > that it's going to start using the drives like a raid 0 stripe. How do > the ZFS versions differ in this? Does it immediately start striping all > files in the background on low priority or does it do it as files are > accessed? Does ZFS in any way do performance testing of Currently ZFS never moves a block once it has been written. The whole implementation of copy-on-write and snapshots relies on this. If you add a new zvol to a pool, new data will get balanced across all the zvols but old data will stay where it was. Ideally you should expand pools before they get too full, or zpool export/import them into new pools if you want good distribution over all disks. There have been hints for the last few years of a "bp rewite" feature appearing, but it has never materialized. -- Dan Nelson dnelson@allantgroup.com
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20110410063258.GA10022>