Using ZFS clones with several Application instances

This was an interesting blog entry about E25Ks, DTrace and ZFS.

One thing I was also thinking about, was the performance gains with ZFS clones, when running several instances of Applications using mostly the same data.

Quote:

"Then came a flash of inspiration. Using clones of a ZFS snapshot of the data together with Zones it was possible to partition multiple instances of the application. But the really cool bit is that ZFS snapshots are almost instant and virtually free.

ZFS clones are implemented using copy-on-write relative to a snapshot. This means that most of the storage blocks on disk and filesystem cache in RAM can be shared across all instances. Although snapshots and partitioning are possible on other systems, they are not instant, and they are unable to share RAM."

I had this idea, when I was thinking about using Solaris as a Xen Dom0 and running several identical (at least in the beginning) MS-Windows instances on Xen DomUs. The cloned MS-Windows images would be located on ZFS clones.

Most of the blocks would then reside in the memory of Dom0. I guess this would certainly improve performance.

The OS images could of course be also served over e.g. ZFS iSCSI Target devices, but the effect would be the same...

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