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... but only if we *have* to! During the initial gather for balance we prefer to avoid replicas on over-weight devices that are already under-represented in any of it's tiers (i.e. if a zone has to have at least one, but may have as many of two, don't take the only replica). Instead we hope by going for replicas on over-weight devices that are at the limits of their dispersion we might have a better than even chance we find a better place for them during placement! This normally works on out - and especially so for rings which can disperse and balance. But for existing rings where we'd have to sacrifice dispersion to improve balance the existing optimistic gather will end up refusing to trade dispersion for balance - and instead get stuck without solving either! You should always be able to solve for *either* dispersion or balance. But if you can't solve *both* - we bail out on our optimistic gather much more quickly and instead just focus on improving balance. With this change, the ring can get into balanced (and un-dispersed) states much more quickly! Change-Id: I17ac627f94f64211afaccad15596a9fcab2fada2 Related-Change-Id: Ie6e2d116b65938edac29efa6171e2470bb3e8e12 Closes-Bug: 1699636 Closes-Bug: 1701472 |
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|---|---|---|
| .. | ||
| __init__.py | ||
| test_builder.py | ||
| test_composite_builder.py | ||
| test_ring.py | ||
| test_utils.py | ||