You'll want it on (Especially on an E5). Its not vCPU's when Hyper-threading is on. It takes the pipeline and splits it allowing to to process two thread per core. Its way better than when it first came out.
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Does it not remove old backups? The first thing that came to mind when that option was presented was that it would remove the oldest backup automatically.
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OK one way to make this more usable is to just fail the migration if the disk image isn't visible from the target node when using storage marked shared?
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