I actually ran into a situation where I needed to concatenate LUNs last week. In my case, the Sun 2540 storage arrays don't yet have the ability to create LUNs over 2TB, so to use all the storage within the array on one host efficiently, I created two LUNs per RAID group, for a total of 4 LUNs. Then we create two stripes (LUNs 0 and 2, 1 and 3) and concatenate them. This way the data is laid out contigously on the RAID groups.
-Aaron On Mon, Sep 22, 2008 at 11:56 PM, Nils Goroll <[EMAIL PROTECTED]> wrote: > Hi Darren, > > >> http://www.opensolaris.org/jive/thread.jspa?messageID=271983񂙯 > >> > >> The case mentioned there is one where concatenation in zdevs would be > > useful. > > > > That case appears to be about trying to get a raidz sized properly > > against disks of different sizes. I don't see a similar issue for > > someone preferring a concat over a stripe. > > I don't quite understand your comment. > > The question I was referring to was from someone who wanted a configuration > which would optimally use the available physical disk space. The > configuration > which would yield maximum net capacity was to use concats, so IMHO this is > a > case where one might want a concat below a vdev. > > Were you asking for use cases of a concat at the pool layer? > > I think those exist when using RAID hardware where additional striping can > lead > to an increase of concurrent I/O on the same disks or I/Os being split up > unnecessarily. All of this highly depends upon the configuration. > > Nils > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
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