r := &rebalanceMeta{
		ID:        shortuuid.New(),
		PoolStats: make([]*rebalanceStats, len(z.serverPools)),
	}

	// Fetch disk capacity and available space.
	si := z.StorageInfo(ctx, true)
	diskStats := make([]struct {
		AvailableSpace uint64
		TotalSpace     uint64
	}, len(z.serverPools))
	var totalCap, totalFree uint64
	for _, disk := range si.Disks {
		// Ignore invalid.