On Sun, Apr 26, 2009 at 3:52 PM, Gary Mills <mi...@cc.umanitoba.ca> wrote:
> We run our IMAP spool on ZFS that's derived from LUNs on a Netapp > filer. There's a great deal of churn in e-mail folders, with messages > appearing and being deleted frequently. I know that ZFS uses copy-on- > write, so that blocks in use are never overwritten, and that deleted > blocks are added to a free list. This behavior would spread the free > list all over the zpool. As well, the Netapp uses WAFL, also a > variety of copy-on-write. The LUNs appear as large files on the > filer. It won't know which blocks are in use by ZFS. It would have > to do copy-on-write each time, I suppose. Do we have a problem here? > Not at all. > > The Netapp has a utility that will defragment files on a volume. It > must put them back into sequential order. Does ZFS have any concept > of the geometry of its disks? If so, regular degragmentation on the > Netapp might be a good thing. I assume you mean reallocate on the filer? This is run automatically as part of weekly maintenance. There are flags to run it more aggressively, but unless you're actually seeing problems, I would suggest avoiding doing so. > > > Should ZFS and the Netapp be using the same blocksize, so that they > cooperate to some extent? > Just make sure ZFS is using a block size that is a multiple of 4k, which I believe it does by default. I have to ask though... why not just serve NFS off the filer to the Solaris box? ZFS on a LUN served off a filer seems to make about as much sense as sticking a ZFS based lun behind a v-filer (although the latter might actually might make sense in a world where it were supported *cough*neverhappen*cough* since you could buy the "cheap" newegg disk). --Tim
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