Date: Thu, 19 Jul 2007 20:27:43 +0100 From: Doug Rabson <dfr@rabson.org> To: freebsd-fs@freebsd.org Cc: Pawel Jakub Dawidek <pjd@freebsd.org>, Mark Powell <M.S.Powell@salford.ac.uk> Subject: Re: ZfS & GEOM with many odd drive sizes Message-ID: <200707192027.44025.dfr@rabson.org> In-Reply-To: <20070719181313.G4923@rust.salford.ac.uk> References: <20070719102302.R1534@rust.salford.ac.uk> <20070719135510.GE1194@garage.freebsd.pl> <20070719181313.G4923@rust.salford.ac.uk>
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On Thursday 19 July 2007, Mark Powell wrote: > On Thu, 19 Jul 2007, Pawel Jakub Dawidek wrote: > > On Thu, Jul 19, 2007 at 11:19:08AM +0100, Mark Powell wrote: > >> What I want to know is, does the new volume have to be the same > >> actual device name or can it be substituted with another? > >> i.e. can I remove, for example, one of the 448GB gconcats e.g. > >> gc1 and replace that with a new 750GB drive e.g. ad6? > >> Eventually so that once all volumes are replaced the zpool could > >> be, for example, 4x750GB or 2.25TB of usable storage. > >> Many thanks for any advice on these matters which are new to me. > > > > All you described above should work. > > Thanks Pawel. For your response and much so for all your time spent > working on ZFS. > > Should I expect much greater CPU usage with ZFS? > I previously had a geom raid5 array which barely broke a sweat on > benchmarks i.e simple large dd read and writes. With ZFS on the same > hardware I notice 50-60% system CPU usage is usual during such tests. > Before the network was a bottleneck, but now it's the zfs array. I > expected it would have to do a bit more 'thinking', but is such a > dramatic increase normal? > > Many thanks again. ZFS does a checksum on every block it reads from the disk which may be your problem. In normal usage, this isn't a big deal due because many reads get data from the cache.
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